Sit back and get comfortable as I try to explain whats going on with my car.

First let me take you back a couple of weeks ago to when I was at Island dragway doing some shakedown runs. I was having a hard time coming out of the whole, ususally I pull 1.7s - 60's with a quick slip off the 2-step but my best that day was a mid 1.8 with a looong slip of the clutch. I wasn't able to figure out what was happening until I looked at my boost log and noticed that I was only making 1-2psi instead of the 5-6psi I usually see. Also at the top of first gear I was making much less boost then normal, usually first gear has the highest boost spike out of the entire run. I was only making around 18psi instead of 22-23 like normal.

Below is screen shot of the log showing what I'm talking about. the top one is how I usually launch, notice boost is good while launching and spikes high at the end of the gear. The bottom one is the one I'm talking about with less boost all over.





I thought that maybe my MBC wasn't working correctly so I switched it out for another good unit that I know works but that didn't fix the problem. Then I tried switching how the MBC was hooked up, its a Tial 38mm WG, but that didn't have make a difference either.

THis doesn't just happen when I try to launch on the strip, but also during normal driving on the street. Say my boost is set to 19psi, if I go WOT the boost might only climb to 15-16psi and just sit there. Then all of a sudden it will SPIKE up to 19psi where it should be. Below is another log showing what I'm talking about.





Notice I'm WOT and boost starts to settle around 14-15psi and then all of a sudden it jumps to 19 where it should be. It doesn't do it consistantly, I'd say maybe 75-80% of the time I go WOT. I don't believe its the boost contoller at all, I'm leaning towards the WG being bad but I want to see what other people think.


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Ok so that was just the one problem. Its not why I made this post but I think it might be related to the other more serious issue I'm having now. This new problem just started to manifest itself last night as I was out trying to diagnose my boost issue described above.

What just started happening is now when my boost spikes, like I described above, my A/F ratio is spiking now too instead of dropping like it normally would do. The A/F only spikes though when the boost spikes and so far I can't tune around it. And as an awesome side effect when the A/F spikes its also giving my SERIOUS knock counts, yah!. I have one log w/32 counts of knock and another with 20 counts. Below is another log showing the boost spike and the A/F spike from last night. You'll see they follow each other perfectly.



Usually when load increases I have my maps scaled to richen everything up and add timing. This has worked great until this boost thing started happening, now its like the ECU has a mind of its own. I'm hoping someone here has seen this before and maybe has an idea of what is going on.

A couple of possible things I think might be the problem are:
faulty WG - although ususally when they fail, which isn't very often, they stay closed instead of open.
bad gas - but I've been filling up at the same 2 stations for months and never had an unusual knock issue. besides that doesn't explain the boost problem.
bad walbro - its pretty new, maybe 20k old, but that also doesn't explain the boost issure.

For reference my setup is a 100% stock block 04 GSR w/ a gt35r, 1000cc injectors, tail 38mm WG, walbro fuel pump, 3" exhaust & obviously ECUFlash. I have zero boost leaks and I'm only running 22psi on pumpgas.