Well, I think.... it sounds like a timing problem. Best I can say without being there is grab your dizzie while holding it about 2500 rpms and ease both ways till the engine levels out good. And put a light on it. Do you have enough carb. solid or hydraulic cam and is it set up right preload/clearance, did you check coil bind, did the cam break in without wiping a lobe. Do you have fuel pressure, check your plug wires for firing order. 18436572, all odd on one side even on the other side. (Don't laugh, I have seen people wire like a F**d.) Make sure carb. is flooding out also