If you don't mind spending the money for premium, get an Overkill tune (they're 50 bucks off until Friday, so after you return your current PCM, it costs 100 bucks). He can then dump codes for a bad cat and you can get a ZZP downpipe with a highflow cat. It opens the downpipe to a true 2.5", adds a highflow cat and removes the U Bend, plus it's stainless, so it'll last for quite a while.

 

A clogged cat is a definite possibility.
If you have access to a scan tool that reads mis-fire data, you could see if only a couple cylinders are mis-firing or if all of them have recorded issues.

At 100,000+ miles, some GOOD maintenance should be done:
- Change Fuel and Air filters (should have been done already, but if not, change them now.
- New spark plugs (AC Delco or NGK, NO BOSCH), new wires
- Change your transmission fluid and filter

The first two items could also being playing into your problems.

 

I agree on the cat and the downpipe.

You'll gain some HP on the butt-dyno and the exhaust will smell good for a couple of weeks haha

 

87 regular all the way, mate.

 

All of the information here is great.

Run the 87, get the cat checked out. Since you just bought the car, I would also do the tune-up anyway. The stock platinum plugs are only estimated for about 100k miles anyway.

Stick with stock parts for the ignition system. ACDelco plugs and wires, shouldn't have a need to change the coil packs.

 

Once again...thanks everyone~!

Just picked her up from muffler shop...totally clogged cat!!

Ubend delete and high flow cat for 200 cash.

OMG OMG OMG I love this car even more. Totally different!!! I thought she was just a little doggy but now that she can breath...this car is much faster than I expected. Gonna go cruise the tires off for a couple hours.

Next up...gonna do the plugs and wires and fuel filter.


THANKS SO MUCH Everyone...this is an awesome community!!!

 

It does smell good funny kinda good

 

High-flow cat is going to throw a P0420 code in probably 2-3 weeks.

You will fail inspection with that code, start looking into getting a tune that removes the code from your PCM.

getoverkilled.ca and zzperformance.com are good for canned tunes.

 

hay chibi mike i said the same thing on the plugs just to see if it could be a bad plug plus what there rated for the miles any way. i didnt want him to spend money on some thing he couldent or didnt have pland for yet to do. sorry i am just complementing the same thing we both said.

 

WE GOT NO STINKIN' Inspections..lol


yea I figured that it would throw a code, I am going to get an wizaired cold air intake that I have been looking at ZZperformance. and probably the zzp1.0 pcm

Once again I just want to thank everyone for the help. It is nice to have so many experts easily accessible.