ECU issue

I have an Mopar performance conversion kit installed for over 15 years and it has worked fine until recently. Sometimes not starting, other times shutting off when idling at stops.
Changed to an Advance auto one and also one I purchased at Carlisle USA made one. Both do the same thing ( Starts fine runs fine but if I rev up to 3000 it sputters and won't go past that. 318 4 speed. I have been told it could be a bad pickup in the distributor but am at a loss. A I said with the orange box when it worked it ran great with no issues.
What is the deal?
Thanks,