2000 Chrysler Sebring Running out of ideas for hesitation

I have a 2000 Sebring JX Convert. With a 2.5l V6 @ 159k mi. A month ago, the wife stopped and gased up, and when she left, the car started to hesitated badly. No codes. I thought it was bad gas, so I drained and dropped the tank, changed out the feul filter, and put premium plus additives (Lucas cleaner in 1st tank, Seafoam in 2nd). No change. Had a mechanic drive it, and was told to start w/ the Cat. Convertor. Had that changed (broke loose inside but not clogged), no change no codes. Changed fuel pump relay, no change no codes. Last Monday, got codes PO0300,0305 and 0306 (random misfires, miss on cyl 5 and 6) The plugs and wires were changed 8 months ago when I had the Timing belt, water pump, seals etc. But I didn't have the Dist. Cap and Rotor changed, so I changed them, ran better but still hesitated. Took to another mechanic who verifed fuel pressure good (59psi) and timing and position sensors in sync, but definite major miss on 5 & 6 only( 60-70 misses over 3 miles driven, versus the 1-5 on 1 thru 4). He said my rear valve cover was leaking oil and probably the plug tube seals were also, fouling them out (none of these gaskets or seals were ever changed). So, after new valve cover gaskets with tube seals, another new set of Champion Plat. Plugs (properly gapped) and a new set of wires, the car ran stronger but still hesitated under load and misses still could be heard in the exhaust at idle, with no codes. The Egr tube port on the upper intake manifold was carboned over, but I cleaned that out. Could a clogged EGR tube cause my problems because the egr valve sounds like its working. Could the EGR valve itself be the problem. O2 sensor? MAP sensor? Clogged injectors? Any suggestions would be greatly appreciated! I am pulling out clumps of hair and loosing sleep here.