What I meant about the pcm 'learning' the pressure:
The key about the pcm learning the high pressure is the way I jumbed the pressure. I fixed it to the desired pressure with a screw. This prevented the two-step pressure that the regulator normally has (45psi idle 54psiWOT). Initially it helped out, but as the pcm corrected the normal non-WOT driving to the high pressure it began to stutter again. I am convinced that the pcm made adjustments to WOT injection because when I would step on it, I would get some pinging up around 6500 rpm that was not there when I had the "two-step" fuel pressure. The pcm definitely counts on the pressure jump when you go WOT, I've proven that to myself on numerous occasions.
Now all that said, I haven't gotten any new O2 data with the new exhaust. However, I got enough data before to extrapolate what is going on.
Essentially, with stock intake and exhaust I had no driveability issues, but the O2 data showed that my AF was already lean below the IMRC opening point, then at that point the AF went from lean to a little too rich.
When I fixed the pressure with a screw, this had the effect of leaning out the AF above the IMRC point because it didn't have the 2-step change in pressure. That leaning out evidently put me in the right AF value for that rpm range because I had lots more power.
With the exhaust down at the y-pipe on the dyno:
The AF ratio for the whole rpm range just got leaner by a few points, but had the same overall shape. I lost torque below IMRC point because it was way too lean at that point, but the AF ratio was pretty good above the IMRC point and that is where I made so much power.
So here I am with the open exhaust having a product of those problems. I am too lean below the IMRC point and pretty good above the IMRC point. THerefore I get a lot of power above and stuttering below.
So how do I fix the problem?
Maybe an SAFC, but the new MAF is going on first.
If the MAF has no effect then I will have to go get an SAFC.
I'm really tired of waiting though.
warmonger
