If in neutral I can rev to the limiter but if driving it cuts off at about 5k. Any ideas?

 

could be a list of things, here are some things to take a look at..

if you have an msd box or the like it could be going out, swap with a freind or hook the factory ignition back up.

arching plug wires or cracked porcelain cracked on plugs.

failing coil

faulty dizzy more prone with aftermarket units.

check your fuel pressure under load

valve springs.

 

Try a fuel filter first. I've seen them do this. Cheap and easy thing first.

 

Weak coil should be added to the list.

 

Still running OG fuel filter soooo it could be that. It's been a while for the plugs too.

 

Yeah my coffee truck did that - after they switched to E10 for the winter (back in the 90's) it loosened all the crap out of the tank and plugged the filter. Started great, ran pretty good around town, but put the pedal down and it was starving for fuel. The old filter felt like it weighed about 3# lol.