i just bought an 87 jimmy, i have no information on whats been modified other then what i can see which is longtube headers, true dual exhaust, and an msd coil, its a 350tbi. when i got it home it idled really high and the distributor wasn't tight, so i re timed it, tightened down the clamp. now it idles a little rough and when i barley give it gas it lopes like it has a cam, but when i rev it up it sounds really healthy
today i took off the throttle body, replaced the gasket, replaced the vacuum hose on the back of the manifold because it was collapsed and dry rotted, replaced the AIC, checked the EGR (checked that it wasnt seized up) and its still loping at very low throttle. does this mean the previous owner put a cam in? or am i missing something here? it has alot of power under throttle, shifts fine, dosnt smoke pop or shake....im lost. any imput would help.
sorry about the lenghty post, just trying to give as much info as possible

 

If the engine isnt shaking,no shuddering,chugging etc when driving,id say its cammed and have fun with it.