1997 Chevy Truck Misfire P0300

Ok I started with the basics, fuel is a solid 55-60 even under load driving. I diagnosed the Ignition module as bad (had it tested) failed low and high rpm. I then replaced the wires, cap, rotor and coil. Before and after I replaced all of those I have an intermittent spark issue. I am using and adjustable spark tester and its set at approx 35k. Its a clean blue spark but it misses every few sparks. The truck has been around a lot so am I looking at cam and crank sensors? The gap in spark gets worse as rpms go up. Also it runs just fine when its cold up to about 1/2 mile, then it chugs and doesn't wanna move.