the stuff I explained just now is still good stuff to do regardless... but...
Since you now have a fuel pressure regulator do me a favor and try getting your fuel pressure down under 5psi at engine idle rpm (750-ish) and see how she acts.
You honestly don't need more that 3 psi even if you were making wide open throttle runs on 1/4 mile.
This all started when you switched pumps.
that should always be the first question when trouble shooting "what did I change or do different that might have caused this"
Try that first, fuel pressure.
