I've searched but every thread I find is for cars with significant mods.

I have a stock 05 and yesterday I put on my downpipe. I have no boost controller or any other mods at all. I am running only the long DC downpipe, no cat, and no exhaust. I obviously have a CEL for my secondary O2.

It ran fine for most of the night, but towards the end I was getting a backfire at 6000 rpm in 3rd and 4th gear. Never in 1st or 2nd. Its just a quick misfire, then it continues to pull to redline after that. Its a really short backfire.

In 1st and 2nd my gauge is showing 21 psi and falling to 16 just like normal. In 3rd I'm seeing a spike to 23 psi and falling like normal. But it doesn't backfire on the spike.

Outside temps are 25-40 degrees and I'm on 93 octane.

Any ideas? I've read fuel cut, boost cut, ignition cut...etc, etc. I would just like to know what the ECU is really doing and why its doing it. I've read that the MAF is seeing too much airflow and so the ECU cuts fuel.

I'd much rather the damn thing cut ignition and not fuel!!

 

Its good to see this is such a common problem an no one has a definite answer. I searched and there's 10 different takes on what is going on.