Answer to Black H6:
The cold air intake I built myself, basically it is 3 " mandrel bend mild steel tube running from the air resivoir at the back of the engine and out thru the hole in the RHS gaurd. Inside the gaurd I have a K&N cone filter mounted up high to avoid water. You get a fair amount of intake noise but the benifits are worth it. The exhust was a trial and error thing - man these H6 engines are noisey. I have 2.5" mandrel bend stainless running from the heads back to a Y junction at the rear of the engine. To reduce noise I had to put in a balance pipe about 12" back from the heads. Behind the the Y junction I am running a single Hi-Flow 2.5" Cat then a 24" x 4" resonator. Thru to the back in 2.5" and a single 14" straight thru muffler with a 4" tip. The best part of doing this is that it has moved the whole power curve and I am getting a big benefit below 3000rpm. Will try and post some pics late on.