Engine is a stock 5.0 with bolt ons. RJM harness, MAF system, with all non-essential systems deleted from harness by RJM, with EGR resistor built into harness. GT 40 intake, 65mm TB, and 70mm MAF sourced from a 95 5.0. MAC headers, OR-X Fresh tune up. New fuel tank and pump Recent module and coil Recent injectors Recent O2s No vac leaks, strong vacuum on gauge. No misfire on wires, or injectors, new plugs. No codes About the only sensor that has not been inspected and cleaned/replaced is the IAT. The car was idling very rough, but intermittently. No one cylinder showed a misfire or bad injector. It wandered, and we went to the IAC. It is working and only had very slight oil (it is recently new) coat, not clogged or dirty. Then we did the tune-up. That temporarily quelled the issues. For a short time, it ran smooth and strong. It is still running MUCH better most of the time, but the ghost in the system comes back intermittently. Idle drops, gets rough, and the car comes very close to stalling on right turns. Not every right turn, and never on a left turn, hill, or bump. Only right turns. The problem is more pronounced by far when the engine is up to operating temp. No mechanical noises, smokes, smells, etc. If it does stall, it starts right back up, and runs perfectly smooth for a few minutes. It never starts right back up and go right into the rough idle that just stalled it. It does it worst on hot days. The idea of vapor lock did cross our minds??? Fuel pressure 38 psi on gauge, vacuum unhooked. Engine smooths out as RPM goes up. Any ideas? We have done alot, I may have forgot something.