I know that the resonator and cat are not very restrictive but I was wondering if you all knew about how much extra horse you would get with a 3"down pipe, cat, Ubend and resonator removed? How much extra total horses for all this?

5-7 tops.

The u- bend replacement has a proven 5hp gain at peak, resonator delete will give you no hp gain but will increase sound leval a bit, the down pipe is a variable depending on other mods,it can yield up to 12hp .

I believe with a Random Technology system, they say you can net 8-9 hp, but as always, results may vary.

Yes, the R.T. Cat is supposed to be up to 8 HP. I installed the RT Cat (which inludes the downpipe and u-bend removal) and Borla's Cat-back exhaust on my '98 GTP two nights ago...Some people say that you won't feel a difference with an exhaust upgrade such as this, but I definately do. This upgrade increased power significantly by reducing KR, therefor letting the rest of my mods perform closer to their peak performance. I noticed the most increase from about 30-55 MPH and 70+...If I had to estimate, I'd say my RT Cat and exhaust helped add about 15 HP. I wish I would've done a run with my brothers Passport GT2 G-Timer BEFORE I installed it though...oh well, I'll have that info for ya guys soon...

Remember that most of the numbers thrown around are engine horsepower, not wheel.

Actually, Random Tech. claims 9 hp and 9 lb/ft at the wheels, so that seems like a pretty good claim, although by itself the converter package is $300+. Pretty nice though.