missfire

[mr2sc89]

my s12 starts to misfire under presure at 3000rpm
but then all of a sudden it could go away for a second and then its back.i was at tiperary race way last thurs day and drifting the oval it missed and i lost power a spun into the wall at 60 . not too much damage! rear bumper? it was running on denso plugs, so i changed them to the ngk gaped them and the problem got worse, ive checked for boost leaks as said, and i replaced all plug leads inc king lead. now this is the max power silvia so i dnt know whats done to the engine, the wireing is in a mess and ive replaced some of it. any ideas?