Missfiring

[smoker]

Hi Hope your all having a good Christmas , I took the Silvia for a run on Christmas eve and it started missfiring badly at about 3000 rpm under heavy acceleration. It will run perfect all day until i press the accelerator and get the boost pressure up then i have to back off the throttle to stop the missfire.

Took a look at it today and the intercooler pipework looks ok and I swapped the AFM over too which made no difference. If I return boost pressure to standard 9 psi the missfire goes away... . If i increase the fuel rail pressure to 40 psi the missfire nearly goes away but still coughs a bit at 4000 rpm and doesn't have as much power as it did . Somethings gone wrong it was running perfectly and i'm out of ideas. Any help appreciated