I have been trying to sort this out for a while now. I got my car dyno tuned in July, made 390whp on a single E85 map. The car pulled hard and smooth after that, and very fun to drive. A few weeks go by and i started to notice occasianlly the cel would flash under moderately heavy acceleration ( not WOT more like acc to highway speed)it was also 3.5k around 10-15psi. I didn't think to much of it being it was not a common occurrence amd didn't happen under wot. A few weeks go by and I changed my clutch (was still on original stock clutch) and drove it very conservatively for close to 600 miles. After i finally got some miles on the mew clutch I went to heavily accelerate one night after work and again cel flashing. Later that night I tried to do a pull (first one in weeks) and got flashing cel and the car Definetly was hesitant. I always let off the throttle as soon as it flashed. I then tried to diagnose the issue
Boost leak test was good
No exhaust leaks
New spark plugs
Pulled injectors and they where clean
Pulled fuel pump and it was clean
Ran a bottle of seafoam through the gas
Double check to make sure downpipe cleared (to rule out vibrations)
Ethanol content is always at 83%
Today I changed my knock sensor to rule that out as well and took it for a drive
The first partial throttle pull I did (2nd gear ) I got flashing cel at the same rpm. Did a few more heavy throttle pulls (not WOT) and did not get a cel. Turned around and did a few WOT this time. The car pulled and no cel but that's when I noticed i was only getting high 12 low 13 under WOT.
My car was tuned to 11.2-11.4 under wot originally so i am starting to think I'm having fuel delivery issues. The car is still turn key start, idle and cruise are fine and I still daily drive it.
Mods are
272 cams (Kelford intake hks exhaust , long story )
Crower springs and TI retainers
Evo 9 turbo
Custom 3in turbo back straight pipe with hood dump
Aem wideband
Turbo smart boost gauge
Grimmspeed boost solenoid
Ams lower intercooler pipe
Universal 4x28x12 intercooler
Stock cold side piping
Hks ssqv
Walbro 255
Stm fuel pump rewire kit
PTE 1200cc injectors

Fuel pump was purchased new, so hopefully it isn't on it was out already. injectors where used. I doubt the Issue is the tune being the car was fine after that for a while.

What else should I be looking into, I really wanted to get it to the track before the end of the season

 

walbro 255 for e85? maybe not good enough?

also check CAS sensor

 

It was fine for a while with the 255. I have not checked the cas. Not so sure how to I'm not good with wiring and electrical.

 

Sounds the like fuel pump is dying

 

Did you let the car sit at all?

My thoughts are fuel pump is going bye bye (As stated above) or the injectors need cleaned.

The knock CEL is a double edged sword, it could be false knock with you being on E, or you may just have 1 lean cylinder causing the AFR increase and a miss.

If you can get a fuel pressure gauge to monitor and see if FP is dropping on boost, that would be my next step.

 

The car does not sit, it's daily driven. At most maybe a day with out driving. But now that you mention sitting I just got back from vacation. The car sat for about a week. When i first started it it turned over studderd then died. When I restarted it it turned over and sounded like a Subaru for 30 sec or so then was fine after that and has been since. I didn't think a walbro would fail only with in a few months.

Testing fuel pressure was my next guess but wear do i tap for the gauge pre fpr?