Re: exhaust woes
oooh yeah, exhaust mods are a great way to customise your vehicle to suit you, depending on the design of the extractors/pipe(s) you go with you can make the engine make torque where your driving style requires it. It's not just a simple matter of peak KW, in fact one guy one here that I'm aware of (JC, ex owner of an AU XR6 VCT) installed an exhaust which actually lowered the RPM at which peak power arrived, but substantially fattened his torque curve to that point. Admittedly the VCT engine is an out of the ordinary case, but it makes a valid point. More specifically, you can get extractors which are designed to maximise low end torque, ones that are designed to maintain a decent increase in torque throughout the standard powerband, etc. In my limited unserstanding (guys, please correct me if i'm wrong in any way, it's the only way I'll learn :-)), the easiest (and I think cheapest) way to get an increase in peak power for the I6 is with a cat back system. I know one bloke who has an XH longreach with a catback sports system and good tyres as the only real mods and it goes/sounds as good as most 8's around here (possibly a freak engine, definitely a good driver). Anyway, I digress. The best thing to do would probably be to ask around several different exhaust places, and gauge their responses. Also this forum really is an awesome bank of knowledge if you manage to prod the residents into responding with tales of their experiences. Also try doing a search of the I6 forum for exhausts, might find some info as there has to have been a thread on something like this before.
Good luck man,