Experts- need some serious help
 

Ok, my car is doing some wierd crap between 2500-4000 rpm when attempting to throttle through that powerband. It almost feels like im lossing ignition and will buck/stutter really hard. It reacts better if I just stab it when im in that range but still has a stutter. Its almost nonexistant on the dyno due to being wot at an earlier rpm range(2k) and it will just push through.

Tuner has looked at it 3 times and swears there is a mechanical issue as he has added fuel/removed fuel, advanced timing/removed timing etc. I have replaced plugs, plug wires, coils, throttle body(TPS sensor), checked fuel pressure. Im not sure where to go next... I thought maybe it was in the harness, but im throwing no codes. Help!?

attached is a snap shot of whats going on in the datalog. You can see fuel trims going super positive and Knock going through the roof while pulling 4-10 degrees of timing. We have checked everything physical and cant seem to locate anything causing the knock.

one common I noticed going through my log and reviewing every event is that it happens at the 38-41% TPS everytime no matter what gear

Car is on E85 & meth

Have you checked anything in the fuel system yet? And have you filled up since the issue began?

When I was involved in the import game E85 was the fuel of choice for lots of STi owners, and a bad batch of corn can lead to symptoms very similar to this.

Ive dropped the filter and it was clean, have also had my ID2000 injectors cleaned. I have been on about 6-7 full tanks of fuel from 3 different stations.

Gotcha, I really thought I was on to something there. What plugs are in it?

currently BR7ef gapped at .028, previously had TR7ix and did it with them only after head swap/retune.

Little weird how the map spikes just before you got that big knock

Have you tried replacing/cleaning the MAP/MAF sensors yet?

Brand new maf sensor. Was gonna swap the map with a known good one tomorrow.

Solid plan. Like motion427 said, that little MAP spike just before the big KR kick-in is slightly iffy-looking. Let us know how that ends up going for you.

You could also try a warmer plug, if you are mostly just driving the car, try the ZR1 plugs. I had random misfires, car breaking up, coughing, etc. and it went away with the plug change to ZR1s.

The timing is probably being pulled due to the knock. I don't really get why your AFR stays the same while your going into boost. It looks like it just stays at 12.5 right through that log.

It isn't hooked up is why. Warmer plug would not solve this. It isn't a slight misfire, it is breaking up pretty badly.

Why log and look for this issue with no wideband. If its lean it would show the symptoms described. Knock and breaking up.

My car did something similar and it turned out to be a loose passenger head ground... It would just fall on it's face and then pick right back up and buck back and forth.

It doesn't sound like you have the exact symptoms I did but it is something to think about. I replaced plugs and wires in my quest... turned out they were fine.