[NiteProwlerSS]

First thing I would check is plug wire routing, may have a plug wire crossed, especially on the passenger side because the wires go behind the alternator bracket. Its easy for them to get flipped. Been there and done that, lol.

What brand optispark did you put on? I always heard horror stories about the parts store optis. I changed optis a couple times but always went with gm.

I do remember putting an Advance Auto Parts coil on my old LT1 car and it would break up at higher rpms, put a new gm coil on and never had the issue again.