Engine rough when at temp.

Could be many things, are there any fault codes stored? When the engine is warmed up, the system is in closed loop, meaning the fuel mixture is being adjusted according to the signals from the o2 sensors, so there may be a problem with an O2 sensor, but there are many other possibilities as well.

I am having the exact same problem with my 96 GMC 5.7. It will start cold, run perfect for about 10 or 15 min then once it warms up it starts running very bad, Backfires when you give it gas then eventually dies. After letting it set for about 10 to 15 min. It will restart easily. But not until it cools off again. Parts replaced and thrown at it with no sign of improvement: plugs, wires, distributor cap, rotor, cam shaft position sensor, crank shaft position sensor, coil packs, coolent temp sensor. fuel pump, EGR, Ignition control modual. It does not have cats as it is an after market exhaust and cats have been removed. Fuel pressure guage reads 60 psi, What is left?