2002 Chevy Monte Carlo Multiple Symptoms

Hello, This car has an intermittant problem. Randomly at idle it will sputter and die or sputter and rev to catch itself from dieing. It will also hesitate at take off and surge at any speed/rpm. I replaced the fuel filter, air filter, and MAF with no change. Dealership said they saw it losing signal to a pair of cylinders so I replaced the ignition module, coil packs, wires, plugs, cam sensor, crank sensor, and PCM with no change. Also, the fuel pressure readings are 1 psi below normal (52psi) key on, engine off but when running, the pressure is well within spec at 45 psi. When it starts to die, the idle psi stays the same initially and then goes up as the engine revs to catch itself. A vacuum test apeared normal when I was checking for a plugged cat (no rotten egg smell). Oh yeah, no codes. Last but not least, there was a 50 mile drop per tank in economy about five months before these symptoms started. Any help would be greatly appreciated.