hey guys i got a 91 k5 350 tbi. this prob been goin on for yrs but getting worse here lately. after running it kinda hard or playing wit the throttle it will start to idle real low like shes strugglin to stay running, if i pop it in nerutral rev it up for a lil bit, then wham it magically clears up and goes back to running good. any ideas or things i could check.?