For many months now i've had idle surge and could not figure out what was causing it. After replacing several parts unecessarily (EVR, DPFE, EGR Valve, IAC) I finally figured it out. The high pressure cut-off switch on the high pressure a/c line had alot of dirt and water inside causing it to short out or something and cleaning it out made the idle surge go away. Apparently the switch was sending incorrect signals to the PCM making the idle go up and then down. The water and crud must have gotten in there one of the many times I cleaned the engine. Anyone who has this problem should check it out, it was a very cheap fix since it didn't cost me anything to clean it out.
