Ive done an extensive amount of searching and have not found a similar problem.
My 04 wrx missfires under boost in all gears, problem worsens in 2nd and 3rd gear. Cel like says missfire on #4. Prolem seems to lessen after motor has ran for an extended time. I feels like the rev limiter hits at 4-5k rpm.
Put new plugs in. cleaned MAF. Took out intercooler and refitted all turbo and intake hoses. New fuel filter. cleaned the sock on the fuel pump. Tripple checked vacum hoses. Put some good octane boost in. new full tank of gas. cleaned air filter.
Car turned 45k mi.
No BOV, factory flywheel.
Sti fuelpump and injectors.
vf54 turbo. Catless up/down pipe
perrin Intake, exhaust.
Protune on turbox's ecu.
Boosting around 18psi.
Just put in ngk platnium's 6. wanted one colder 7 but had no patience to order.
I feel like I have covered alot of bases and still the problem worsens. My brain hurts and i have been scouring the area for a sutibale cliff to drive the car off of, need help.