Seem to have been writing this for a lot of members recently...I recommend the following in this order:

1) ST170 4-2-1 Manifold or similar by Millitek or Piper
2) Full cat back from Millitek, Piper, Scorpion, Blueflame, Magnex etc.
3) Enclosed induction e.g BMC CDA or Pipercross Viper. Alternatively source a ST170 airbox complete or just the bottom half, ST170 snorkel and 2.0 auto air deflector and fit a K&N panel filter.
4) Evolution Chip flash map or Dreamscience. Don't recommend Bluefin.

The above should see a PROVEN 140-150bhp. 150+bhp if you have a very strong engine (or if the dyno is feeling a bit generous)