No cat rules that out.

Most end up running around 10-11 psi with those modifications.

Still need to know what ignition products you used. If they were used MSD coils, that would account for the high load misfires.

Side note: there is no chip tuning available for your PCM AFAIK. Flash tuning is what's used. DHP or HPT being the main two pieces of software/hardware to do it.