Alright guys so i have a 89 toyota supra. rebuilt just a few weeks ago it was driving fine , and now all of a sudden when i let off the gas real quickly the idle drops to 500 , and goes back up really quick, during that time when the idle drops the check engine light comes on for a split second. i ignored it , but the next day now it started dying on me on occasion. So any ideas as to what that could be. clogged air filter maybe?