Ignition break up at 4000+ rpm

[Ziegelsteinfaust]

I have a mid 90's Corvette LT1 engine in my C10 with a gmpp 4 barrel intake, Q-jet, and pertronix equipped distributor. The engine was rebuilt with 10-1 compression, and not the factory 10.5-1. The heads are gasket matched to the intake, slight porting, and back cut valves.

The truck pulls hard to 4000/4500 rpm where it just rolls over, and you can hear then engine kind of make a bum bum bum sound.

Right now I am convinced it's ignition break up because a bad module.

All plugs check out fine, and the timing light works on all cylinders.

The truck drives great under normal circumstances, and mpg is right where it roughly should be. I have no issues hauling heavy weight either.

Any ideas on something else to check?

Or at the next oil change. I am going to just put the distributorless ignition back in.

[Willshook]

Making sure the Pertronix has 12V would be my first check.

I wouldn't go back to the OptiSpark for anything...