fuel or timing problem
 

i was racing the car today and in one of the run my car stumble real bad somewere around 6200 rpm and smoke and look like spark coming from the muffler to and the boost gauge was up and dowm like crazy. i dont know what wrong, never done it before this is the first time that done it. what it could be timing or fuel? please help

PS is a 84 gslse with a 13b gslse engine weber carb stock turbo II turbo running 11 psi

was the smoke black or white?

it might have lean-popped or if your ignition is weak or sparkplugs are going bad it could cause that. did the car do it again or only once? since its carburated it might have loaded up and foules the spark plugs.... all are possibilities