Hey Roy,at the moment my exhaust could definately be improved.I used to build custom exhausts and extractors for many cars including a couple of "B" grade V8 supercars so ive got a bit of knowledge.The outlet on my single turbo is 3" which is the size of the dump pipe,in my opinion it should flare out to 3.25 or 3.5 but its reasonable.It runs to a smashed out 3" cat(which I did not do)which again is too small.From there on is 3.5 stainless system,of course all straight through.Some time next year im going to build a better system for it.The new system will be made out of mild steel as its always quieter,and the packing in the mufflers never lasts as long as the stainless pipe and muffler housing,so really stainless is just for show.The only real way to test your exhaust is to drill a hole in it,say just in front of the cat and hook up a pressure gauge.If it moves at all,that means backpressue,and that means power loss,especially on turbo cars.Sorry to ramble on but this has been a passion for both me and my Dad for years now.We have also developed a variable exhaust system using butterflies actuated by adjustable pressure sensors,so you can have the best of both worlds and get rid of that annoying highway drone.Remember your exhaust is just as important as any other performance part on your car,but Im sure you know that,cheers mate