got a 71 el camino with 350. excell hei distributer, msd coil, msd wires, edelbrock carb. when i hit @ 3200-3500 rpm i get a flat spot and boog down then picks up again. what could be causing this problem.

thanks for any help in advance.

Difficult to say. You dont have enough info in your question. It could be accelerator pump bad. Your secondary air valves may open to fast, your timing may be off, you could have timing advance sticking in dist. What you describe is most likely carb.issues. Do you know the history of the carb. ? Did you buy it new? Get it from a friend? Try to get the history of the carb. and know if it has been adjusted for anything else. Good luck. Keep it running.  

the carb was bought new 6 months ago it has been jeted and rejeted i did change the cap and rotor and the popping went to @4500rpm  

If you have access to a dial back timing light double check your initial timing and your advance. If your timing is correct and your advance is working properly you may want to check your valve springs. That would be a rare one one but it could be that you have weak springs or broken springs. Also check your plugs to see if you are running too lean. They will be snow white if you are too lean, they should be just a very light tan color when you have the jetting right. And make sure your carb isn't too big for your application. Hope this helps. Keep looking, dont give up.  

I had a '67 c-10 with a 283 do me that way once but ti was from about 2600-2900rpm  Someone told me that my distributor bushings might  be worn and letting it wobble a bit.  I replaced the distributor and it was fine.