Gut the stock DP
 

I gutted the second cat and Im happy with the slight sound increase. Im thinking of gutting the stock DP now and have a few questions.

Little back ground first. When I got my MS6 early last year I got a Cobb SRI & a 3" intake from I forget what company. Worked out pretty well but I experienced some minor backfires here and there and eventually it killed my top O2 sensor. After putting in a new O2 sensor I played around with intake only and SRI only and either config netted backfires so I left it stock as I was not ready to get an AP and get tuned.

So if I gut the stock DP and use a Spacer for the top O2 sensor can I avoid CEL and not have to worry about an AP/tune? Im just looking to free up the exhuast a get a better sound for free besides my labor.

Lol. "Worked out good but broke my car." In for more fail.
Tons of threads on the proper steps to modding this platform.

Why not just spend $150 and get a Ebay 3" downpipe?

Jason... :sucks:

So how about putting it this way: would a totally free flowing turbo back exhuast with no intake mods require an AP/Tune?

I thought it was funny too that this car couldnt take a full intake without sporadic backfires and then eventually kiling the O2. But as far as I liked it but it killed the car, I meant that the sound and slight performance increase was nice and I could of lived with the little backfires as they only happened a couple times per week.

Did you reset the ecu when you did the intake?

Yes sir! Pulled the battery everytime I tried a different combo of sri & intake.

You shouldn't experience any backfiring because of an intake. I wouldn't be surprised if something else is wrong.

Do you know if it was modded prior to you purchasing the car? Also, why would you even contemplate other mods before resolving a backfire issue?

My guess is boost leak. You losing metered air and gaining fuel for the air that IS making it in, which isn't fully burning in the combustion chamber.

That's what I thought after reading up on the cars. A SRI & TIP seemed to be universally accepted as a largely problem free mod. My Cobb SRI had the straightener and was used but came to me in perfect condition. The ATP TIP was used also but I purchased brand new silicone fittings and used t-bolts for all the fittings.

When I had both in the car all seemed well. I knew from other people that I might get a backfire or "pop" here and there. They kinda annoyed me so I spent a few weekends trying to find any leaks or loose fittings. I got pops with SRI + TIP, SRI only and TIP only. I settled on just running the TIP because it fit well with the stock airbox and I could still feel some performance increase over stock. The SRI made the car too noisy for me. TIP only I would only get a couple pops a week.

But eventually I had a few weird events where the car would stumble and almost die. Each time I checked and rechecked all the fittings and connections and pulled the battery. I started throwing CELs and those turned out to be a dead top O2. So I went back to stock.

I tried the TIP one more time and got one "pop" so I pulled it and havent looked back.

I gutted the second cat because I know freeing up exhaust flow is nothing but good. I'm looking at gutting the stock DP to further free up the exhaust. I know I will need to get an extender or diode for the top O2 but I was wondering if people felt the car needed a tune with a wide open exhaust. that was the intent of my post. I included the tidbit of my intake problems to avoid people saying "dont worry about the DP until you get a full intake done."

Bingo but for the life of me I couldnt find any leaks or bad fittings and I tried SRI + TIP, SRI only and TIP only all gave backfires.

Could I have a leak somewhere else that only causes problems when the intake has more air flow? Maybe a hole in my IC, bad gasket somewhere?

A hole in the intercooler is totally plausible.

I made a post in the troubleshooting section to get to the bottom of this before I gut the stock DP.

your backfiring on decel amirite? can be attributed to your second cat removal. get some sort of monitoring device, check ltft's. nice bump. i highly doubt you fouled your o2 sensor from running that rich.

Between shifts only never decelerating. That happened before I ever touched the cat. Something killed the o2.

Definately going to get some datalogs. Waiting for some stuff to arrive by mail :) I started another thread in the troubleshooting section.

I wouldn't gut the DP till you get a monitoring device. If you free up the exhaust too much, you will probably start to lose fuel pressure and join the zoom zoom boom club. If you want more sound, get a catback.