I had a similar problem in my car which drove me and my mechanic nuts. Until a friend told me to check the fuel pump relay. That turned out to be the problem. In my case, we would hear the fuel pump start up and so we assumed the relay was ok but is was not. It jhad a bad solder point. I was told that when that relay goes bad, a lot of strange things start happening. Erratic, idling, cruise control problems and so on. Hope this helps.

My car now runs like it never has before!