I have a '94 Prelude Si and after i run it hard for a while when i let off the throttle the tach drops to about 4 or 500 then evens out around 800 where it should. It would be so bad except that sometimes is worse than others(it almost cuts off). I tried turning up the idle but it just does it at a higher rpm (drops to about 500 then evens out around 1g. Any ideas what could be causing this? Already tried the stuff on the page about fixing an eratic idle and still screwing up but only after i run it hard for a while then ti keeps doing it until the car sits for a while. Don't know if its a cooling problem or what. Thanx.