+1 for getting it tuned,
My old version 8 when i bought it did exactly the same. Had an exhaust but no tune and it constantly overboosted.
As @boon said, new panel filter, 3-port, fuel pump for good measure and proper dyno tune. Car will be a street animal. Sure @PBMS will be able to do something for you if you say you're from clubsub and do the lot with them