I have a tuning problem with my 1986 Indy 400. I can't set the idle speed after the engine has warmed up. After the engine has warmed up, the idle drops to around 1000 rpm and bogs when you open the throttle. You must first open the throttle untill the idle picks up to about 2200 rpm to eliminate the bog. However, when it comes back down from a run, the idle drops back down to 1000 rpm, no matter where the idle screws are set at. Other than that, it runs fine. Any ideas?