There's a couple threads about that very thing. People always ask me why I don't modify more than I have to, and this is why: just more stuff to go wrong. LOL. With my luck, anyway.

Glad you figured it out!

 

So a bit of a continuation from this issue, as it turned out to be a fuel drama. So I made a few attempts to get my car tuned by Jay and each time we've had to stop because my STFT is at +25% fuel. He suggested a leak somewhere so I did an intake test and I was able to get it up to 32ish PSI before the compressor didn't love it any more but that didn't solve it. So I pulled my exhaust apart down to the O2 sensor and even replaced the O2 sensor and all gaskets but that still hasn't fixed it.

The only difference I have noticed is that before I pulled everything apart when the ECU was adding fuel my wideband was still reading lean (over 20) now that I have put it all back together, the ECU is adding fuel but the afr sits between 14-16 at idle

I thought maybe a fuel issue but I seem to have good pressure (44ish PSI at idle and rises with low amounts of boost that I have been running to test it).

When I blip the throttle to cycle the O2 sensor it drops the trims right down to 2-3% and has even started pulling fuel out on a few occasions.

What am I missing? What have I not checked? I have seen posts from people saying that changing certain exhaust parts can upset the O2 sensor, would this be the case as I am running an external dump? Kinda running low on ideas here

 

To confirm: this is all going on at idle or driving? both?

If your numbers have changed, it's possible you had a leak near the o2 sensor, maybe? How does the car run? When my car had a problem and would randomly idle at 19:1, it would pretty much want to just die.

 

The modified fuel pump housing could still be leaking with the 255, just not as badly as with the 450.

 

Do you have a divided gasket on the O2 housing?

 

Well when driving it goes into closed loop and the STFT will read 0 anyway but with that being said, when driving the AFRs seem fine, especially under load, I would assume that if the fuelling is out that it would really screw with my AFR under load, correct?

If I was still having a pressure leak from my pump housing wouldnt that make it lean out under boost/load?
I only cut plastic away at the bottom of the housing to allow for the wider pump, I didn't actually touch where the top of the pump goes into the housing so I am hoping it's not that.

Yeah i am using a divided gasket on the O2 housing, just in case anyone had had experience with them, I have a MAPerformance pipe.

So before going and changing all those clamps, gaskets, sensors etc when it had the "leak" it would drive just fine under all conditions but when idling the revs would climb on their own to about 2k and hang there. Now I've changed everything, it idles fine but "stutters" under light load and at low rpm so something has definitely changed but I am just wondering if they are actually related or not

 

Thoughts? Anyone? I was hoping to be able to spend time on it over the break but that didn't happen so this week will spend time on it and would be awesome if I could have a fresh perspective