i have an 02 sti with walbro fuel pump ngkpfr7b plugs full decat k and n panel filter and remap by simon at jgm,it keeps throwing ecu light with 0304 missfire on 4.i have cleaned maf about 4 weeks ago any one have any ideas.was thinking of swaping coil packs around to see if missfire moves but its a slow process waiting to reset light,changing coilpacks and then waiting for error code again.any help out there please thanks.

 

forgot to mension it was happening before the map and simon didnt see any problems during map !