I beg to differ with the last post. If you use a well-designed MBC you will not have any problems with "erratic boost". The best MBC out now is the Hallman ProRX.
http://www.hallmanboostcontroller.com/
Be sure to get the one with the ceramic ball. Your turbo will spool faster than with most EBC's. This unit is well-known in the Mitsubishi EVO community as the way to go. Even guys running low 10's in the 1/4 mile with full stand alone engine management use the Hallman.
Have you boost leak tested your car? I built a unit from some PVC pipe and a valve stem (like in your wheels). Just put this in your intake, hook up an air compressor, and pump some air in. If there are any leaks they will be clearly audible hissing noises ( so this in a quiet place as some smaller leaks are fairly quiet).
Good luck!
EVOlutionary