If you don't want to throw parts at it needlessly, have someone check the fuel pressure when it's warm. I've seen many older cars with fuel pressure issues caused by crap lines, crap filters, blocked pickup screens, bad regulators, old pumps or accumulators etc... yet still run okay-ish, but gutless... and have a hard time starting when warm.
Also worth checking for stray sparks in engine bay area at night in the pitch black dark.
Has the engine cam belt been changed? May be mis-timed or slipped. Worth checking cam timing. Compression okay? Trans slipping? Assume that tyre pressures are okay and brakes are not dragging.