Help! Periodically my 96 Elantra idles rough. I've never had any codes but have replaced; fuel pump, filter, injectors, TPS, transmission mounts, plug wires, plugs, fuel pressure regulator and many unrelated items. 90% of the time it runs fine but after driving for 10 or 15 miles there's always a chance it'll stumble for a few seconds with a corresponding loss of power. I have the shop manual and have researched this problem as much as I can. My list of possible root causes is now down to: cam chain (which I can't find out anything about in my Haynes or Shop Manual), MAF loose connection or needs to be cleaned, EGR, clogged cataylitic converter. I am just baffled especially by the absence of codes. When this problem starts it'll persist for a while and I have to raise the rpm's to 2,000 to start from a stop. Any help would be appreciated greatly.