i have a 1993 lincoln mark viii i race it on a dirt circle track i am one of the points leaders and the car has been having a problem were it stumbles when u first hit the gas and then again between 3000 and 5000 rpm and the last time i drove it it was running the worst it ever had then i went out to drive it again about a half hour later i had checked all my coil connections and my fuel injector connections and when i went back out it now will not idle by itself but the stumble has gone away and the car has never been this fast before what could cause this kind of a problem i also checked fuel pressure and it eas good thank u