Cam timing can be checked by having valves of any cylinder rocking, the piston for that cylinder should be on TDC. I had faulty batch of timing gears for sv ford v8 once where timing mark was wrong. Is muffler clear?, if it was a bad oil burner it could be blocked. If all machining was done correctly the fitter checks each component for proper running clearances and fitment, gaskets should be checked and fitted right way round. Any deficiency between valve face and throttle plate will not hold vacuum, any thing under valves will leak compression. You dont state if inlet guides were replaced, they can effect fuel mix if badly worn, generally it is a process of elimination and something major is escaping your diagnosis. Someone said cam timing could be 180o out, that will only affect spark timing.