With the PPP backbox retained the increase in noise won't be appreciable, although the TSL 333 pack includes for a group N backbox from memory. If the cantre section and back box are changed then it will be noisey!

 

Had my 54 plate STI remapped back in 2005,much improved the performance over standard and never given a problem.Never had the car on a rolling road so cant give any power figures.JAY

 

I'll add my 1p worth too. A few of us have had our 05 PPP cars plainly mapped, mine was only done a couple of weeks ago by Andy F and made the expected ~340bhp and around 330lbft, same as Urban and a few others on here. Andy said he gets within about 5bhp using delta dash comparing to the rolling road he uses local to him. Mine was on dastek rollers a while ago and made 315bhp and 270lbft? before the remap.

It's all in the way it drives now though, it really is a hell of a difference. I think bang for buck, it's worthwhile if you don't want to drop money on a new exhaust etc. I think there is some thought though that the 05 cars have something changed in them as they rev harder at the top end compared to the 03/04 cars, this is from Andy too.

I'm certainly very happy with mine and don't think you'd be disappointed.

 

tsl are very good used to take my wrx to them and was always happy! however i would suggest you take it a little further and spend another grand or so on exaust and headers then you will really be impressed with the results and you will have a really quick car instead of just being in the average bracket!! after all 333 in a lardy new age will still get spanked by a 280 ish classic and youll need close to 400 to see off one with 330