Please do feel free to post anything you think will help while shopping for exhaust. Kind of a one-stop shop for researching, ya know?

Just got off the phone with Flowmaster and they had told me that their Series 50 Delta Flow will be aggressive-sounding, with some interior drone. The Series 50 SUV has minimal interior drone.

With young kids that tend to pass out on road trips, I need to keep the res and kill interior drone.

Anyone else have any suggestions for good mufflers aside from Magnaflow, Cherry Bomb, and Flowmaster?

Looking on ZZ Performance\'s website , I see several DPs with and without cats.

should I be looking for OE cat or hi-flo cat? is there any difference?

Also, should I be concerned about not having a rear O2 sensor? Why do we have 2 O2 sensors?

What is the differences between a 2.5" dp and a 3" dp? What works best for what application?

EDIT: Also, all DPs delete the u-bend, right?

Ubend makes room for the rear O2 sensor by bending downwards, causing restriction. The ubend is located just aft of the cat and before the resenator.

are there any kits that eliminate the rear y-pipe? I've noticed that the rear y-pipe is more of a T-pipe, which most likely is causing unneceesary restriction.

OE cat will come with the Ubend.

No you don't need the rear O2 if you put in a simulator or some one knows what size resistor or something like that or have the code removed from the PCM. The rear O2's job is only to check cat efficiency. It has no inputs into engine performance or behavior all it does is turn on the SES light and set a code saying cat isn't converting.

The Ubend was the engineers way of protecting the rear Ubend from road debris. If you can't delete the rear O2 code or don't have the simulator the bungs on the hi flow cats have them mounted horizontally and no one has had any issues with the O2 breaking off.

As for a 2.5" DP and the 3" DP

That is the size of the piping. The bigger the more airflow. Keep in mind the easier the airflow the lower your low end torque will be. But what you lose on low end you make up for in top end. For GTs that won't be seeing a power adder the 2.5" is primo. It'll maintain the low end torque to get the car off the line faster. The top end gains won't be seen unless you frequently flog your car at the track etc. But for day to day fun factor 2.5" But for the S/C'd or turbo'd cars the 3" gives you the flow needed for all the power. They need all the air flow they can get.

See the FAQ on cat or no cat

As for the "Y" in the rear for the two muffs. Yes it's ugly and all the aftermarket "Y"s are custom made. You really won't gain much by changing it unless you are looking for every 1/1000 of a second on the quarter mile. That goes for the entire catback.

50's are way to quiet even with a open exaust( no cat or res!!!

Just got off the phone with Cherry Bomb. The gentleman that I spoke to had advised me to get the car diagnosed BEFORE replacing the cat.

The OE cat is designed to last the life of the car. If it goes bad, there's 7 times out of 10 something wrong in the engine. Could be a leaking/seeping gasket. Could be rich/lean. Could be...

Cherry Bomb does have a direct fit 2.5" DP w/hi-flo cat and u-bend delete. Cherry Bomb\'s products .

Only problem with Cherry Bomb, and they were very upfront with me, is that to install their products, some welding is going to be required. Their mufflers will not "fall in to the car", meaning that the hangers will need to be fabricated or removed and reinstalled. Exception: The DP w/cat is a direct fit OE replacement, and requires no further actions other than R&R.

Yeah, cats fail for obvious reasons, but most GMs crap out sooner or later. Bad design I think. Most normal cats fail due to coolant burn-off or a bad O2 sensor causing it to run rich.

All mufflers require welding to install. They need the hangers placed in the proper places and it's best to weld them to the pipe. I'm running a 3" cherry bomb (26"?) for a resonator. I'm happy so far, when I get the rest of the exhaust done, I'll deliver a final verdict.

There reason no one replaces the factory Y is that, if it is a restriction to you, then the whole 2 1/4" catback is a restriction. Replace it all with larger pipe.

I want a GP GT to mod and keep N/A.

Hows it feel to want? I got one and you dont! lol

Colleen was built in APR 99 and has 128k on her. The cat couldve just...failed? Just like that? Now I really dont know what to do. Replace the cat and both O2s (nm the fact the front is brand new) and see if I have any more issues. Or diagnose, fix, then replace the cat. Or just take the Red Rocket or the Pink Panther as my own. Hmm.

Any rich folks out there wanna sponsor the maintenance and repair of my car for me?

There's been enough random cat problems with the GP that I think saying that it just crapped out is perfectly plausible.

With the Delta Flow 50s, I really think you'll be fine with those, they're the quietest FM I've ever heard. 40s are louder, in the order of Delta Flow, Original, Super of quietest to loudest. So looking at the 50s, they take one of their mellowest mufflers and put DF tech in it? Definitely results in a quieter tone. Whoever you talked to .. really didn't know what they were talking about. T-bat also likes his Summit mufflers, so I'll let him put in his two cents since he's spent so much time going through different exhausts. I didn't get a chance to really hear his Summit ones at TMS; too much noise on and around the track.

If you're really worried about it, get some resonated tips to go with the DF50s and I think you'll be happy with it. My old GT with 40s, no cat and no res'd tips didn't drone as bad as my GTP with res and Super40s, as an offtopic comparison.

CanadianGTP had DF50s and really liked them. I don't think he was looking for anything loud, just something mellow and a bit louder than stock. If you get a downpipe, you'll also notice a deeper, and a bit louder sound. It'll also get rid of your u-bend.

slp has a good cat back exhaust for 500

Catback exhausts are exorbitantly overpriced, and SLP's sounds like ass with headers. Our exhaust systems are not restrictive enough to warrant throwing up money for a full catback.

You can construct your own mish-mash catback for cheaper than a name-brand with the same, or better, results.

x2.

and i still have yet to hear a GP with headers that sounds good.

if you need to replace your cat then I think its only sensible to go with the hi-flow cat. BlackArrow just replaced his with a Magnaflow unit that included D/P, hi-flow cat and U-bend delete in one unit for $142, which is about half what I paid (and I didnt get a new D/P!
My cat plugged and started all sorts of ills all in one weekend, so dont be shocked over that...and mine went with much less miles than your car has on it.
I have rear O2 sim on my car...the rear sensor is only to monitor after cat exhaust temp. After I had my hi-flow installed my car kept throwing codes (low exhaust temp)...The AZ guys kept telling me to replace my O2 sensor but I added the sim and has been fine ever since...to the tune of about 40k miles.
My Summit muffs were cheaper than most others I looked at and I have been very happy with the sound...I actually wouldnt mind it a bit louder but aslong as the drone is gone there will be no complaining from me. Summit also carries a turbo muff that is a huge bargain, but the "fully welded" muff I bought I believe will outlast the others.

Mine sounds stock.

FrankenGP doesn't count.