So when my car fully warms up my scangauge reads water temp at 200-220 degrees. When I stop at a red light I see my revs drop to 600ish, move up to 900, back to 7/800....it idles all over the place and sounds like a peice of junk. I used some Seafoam deep creep in the vacuum hose and the idle definitely improved, but only for a few days. Anyone know what I can do to make it idle properly? Should I be worried about an underlying issue?