Misfires on boost no CEL


New member
Hey everyone I have a 18 STI that?s I?ve recently modded but I?m having issues with misfire when I hit boost and not sure what is it. At first my tuner thought it was an ignition problem so new NGK cold spark plugs were installed and gapped to .025 didn?t fix it, then I changed all the ignition coils and it?s still doing it. The has cars been checked for vacuume and boost leaks and all that were found have been fixed. I also have no CEL and checked ACVS on all 4 and it looked normal , consistent and in sync.

AIG air oil separator
EGR / air pump delete
Cobb big SF intake
TGV deletes
1050cc Fuel injectors
Cobb Fuel pressure regulator
Cobb Fuel pressure sensor
Cobb flex fuel kit
AEM 340 fuel pump
Catless downpipe
Muffler delete


On a quest of STi erudition!
I don't think I can help, but I am interested to find out what the culprit is.

Does your car misfire only when it's in boost? From what you've typed, that's what I'm interpreting.