Rough only during boost

[zack13277]

So I just rebuilt my transmission and drove the car with the stock 8psi of boost setting and it boosted fine no problems. So then I hooked my mbc up and set it to 15 psi, because that's what I had it at before I rebuilt my transmission and it ran great before, but now it runs rough only when I'm in boost it idles and cruises just fine. To me it seems like I may not be getting enough fuel, but I don't know. I did install poly mounts so maybe its just rougher because of that??? Once in awhile the idle will jump from 1200 to 1400 rpm back and forth, may be something else idk.

1990 Eagle Talon TSI AWD

Mods (relevant in my opinion to problem): fuel filter, rebuilt 450cc injectors, stock fuel pump, spark plugs and wires, rebuilt 14b, smic hard pipes(I did not boost leak test), poly mounts

Any ideas please let me know.

 

[Colt4G63 also]

Plugs, wires...

 

[zack13277]

I replaced plugs and wires about 1500 miles ago.

Well here's the thing the car ran fine this summer at 15 psi, but now that its like 15 degrees outside and the fact that I have bigger intercooler pipes do you think that would cause the air to be denser and make me not have enough fuel??? Does that make sense at all or could it be something else, I'm kind of just throwing it out there.

 

[Colt4G63 also]

Yeah the car sucks in more air when it's this cold. When I run 30 psi, I go through a set of plugs every 1500 miles (or less), but I did find that the NGK wires last years. Try a tighter plug gap if it feels like it's missing under boost, if it's knocking and breaking up, turn down the boost.

 

[RickyM95GST]

Have you tried testing for boost leak?