Yes, fuel pressure test, preferably WHILE THE VEHICLE IS ACTING UP. A less-effective but still reasonable "cheat" is to use the bypass button included with most fuel pressure testers, so that fuel flows down the cheap-junk vinyl tube into a drainpan while the engine is running. Simulates increased fuel demand by the engine.
Also, as usual, verify ALL the sensors and computer outputs by connecting a scan tool. In particular, assure that the TPS and MAP sensors are working properly. Wouldn't surprise me to find that a heavy-throttle misfire is caused by a failed TPS that doesn't transmit a proper signal at large throttle openings.
How old are the usual "tune-up" items? Distributor cap 'n' rotor, plug wires, spark plugs, PCV, and ignition timing/timing advance checks, fuel and air filters, etc. Pretty common for weak ignition systems to run OK at low- and mid-throttle, and fall on their face when voltage demand goes up due to higher cylinder pressure when the engine is working harder.