Ok so here's the deal. When my car is under load (getting on the freeway) it randomly misses above 4000. It started happening after I tuned up the car (Motorcraft plugs, FRPP 9mm plug wires, Motorcraft cap and rotor, pcv, and fuel filter). I initailly put on a Ford Racing coil, but that killed my tfi module, so I replaced it with an Accel one, then the car would only rev to about 3900 and acted like it was hitting a rev. limiter. Put the old coil back on and it drove normailly for a few days. Then all of a sudden it starts to miss above 4000, like a light sputter/ loss of power, as opposed to the limiter problem before. Mods are Steeda underdrives, timing advanced, Bassani catback and headers, and a ton of suspension stuff. It also lightly surges at idle, but it's always done that. I'm thinking dirty MAF or maybe the stock coil is on its way out. Any other suggestions? I'm gonna clean the MAF tomorrow if time permits, we'll see if that helps. Oh yea, the car is a '90 Lx 5.0 with and AOD automatic. Thanks guys, I'm stumped.