As I was changing my oil tonight I thought about when the last time I did a PCM Reset. I have never done a PCM reset before and have done the 3" downpipe mod along with plog/poly mounts/K&N CAI and the only one that ever had the battery disconnected (and PCM disconnected) completely was when I did the K&N CAI which was my first mod ever.

So here is the question. Should I disconnect the negative on my battery and let it sit over night w/ negative off battery so I can make sure the PCM Resets?

Also I have a SES light on for the high flow cat and was wondering if I reset PCM if it would adapt to it and not turn on? I'm sure I'm doing some wishful thinking here..

You need to get you 02 code deleted from your PCM for the highflow cat, the light wont go away unless you do so.

A reset won't do you any good now. There have been enough engine cycles for the relearn.

Alright good to know I'll just leave it alone.

I can delete that code in 10 minutes and your car has already learned the fuel trims.

Ya, but whats the damage?

A little bit on gas mileage. Ive heard different sides of it. Some say nothing some say its a little better than running a 02 sim. I guess when it turns off the test it runs a little rich? Idk off the top of my head but I'm sure someone else has a better answer.

Nothing at all, unless you actually remove the rear o2 sensor.

By "damage" i meant cost.

When ever I get my laptop back and when ever you want to drive to my house.

Rear o2 has no effect on gas mileage. Only time it could would be for 01+ with the cat efficiency test, in which case you would be running hella rich.