I have a 93 with a 306 8.6-1 comp, tfs heads and intake, Anderson b31 cam, c4 3500 conv, 373 rear ,vortech si 17 psi, 92 mm pro m, 60lb injectors, aeromotive fuel pump glens rails -10 feed line -6 return, snow meth injection, Anderson pms series 4 with map, msd ignition, dist, 6al and coil. My problem is at around 6000 rpm its starts to misfire BAD!!!! I have changed MSD box, dist, plugs and wires. My afr is at 11-1 when this happens, I've added a little fuel and removed some fuel with no change. Also added a little timing and removed some as well with no change. I removed the supercharger belt and has no change without boost. Tried a different brand of fuel (93 octane with lucas octane booster) Engine temp seems to have no affect on it. Plugs are Autolite 3923 gapped at .028", Base timing set at 10 degrees. I'm drawing a blank....Any help would be GREATLY appreciated!!!!! Thanks Brian.