jon is right, check all your air hoses and Intercooler piping. You would be amazed at what a crack in one your intake hose between the maf and turbo can do.
Since the swap is done, any decent mechanic should be able to diagnose it if you aren't comfortable doing it. They just may not be able to replace anything
Although the motor made a journey accross the ocean, it is still an internal combustion, piston engine so they should be able to figure it out. Try finding a good RX-7 mechanic sometime.