Personally I wouldn't bother mate!
Valved systems are fine where they are an OEM fit on new cars, but why waste cash trying to replicate that on an older car which sounds pretty decent from the box.
Go and speak to Infinity (the guys next to Jim) and get them to custom build a "normal" system for you. I did and I am very pleased with the result.
My old Mongoose was too intrusive at cruising speeds, so Infinity fabricated one with extra resonators at the front, which made cruising quieter from inside the car. They then used smaller silencers at the rear, so the best of the noise is out back. If I want to have a little fun and enjoy the rumble, I just open the windows.
No fancy switches to mess around with, it looks good, sounds good (without the added knob-headed attention seeking function) and only cost £600 all in.
By
RichardS ·
Woof woof
http://www.eden.rutgers.edu/~jionin/dogsout.swf
Tim