I'm hoping that someone can point me in the right direction on this, i have the most peculiar exhaust setup on my westfield with something that resembles spaghetti junction. I am looking for a system whereby i can have an interchangable silencer, one with inbuilt CAT and one without but can be changed for MOT time like a motorbike. Hoping CAT removal and induction will release some horses..........Advice and links gratefully received. :D
This is what I have done with my Marlin - here goes. To release some more horses from my K Series engine it needed 31" primaries, so after much research found that the best company for a stainless steel manifold is Exhaust By Design, bit of a trek but did a superb job. This extra gas flow then gave me noise issues being a fraction under 100dB, the magic figure for track use and too close for comfort. At Stoneleigh I managed to pick up an extra silencer which fitted perfectly where the cat is for £25 from Custom Chrome and this reduced the noise to 95dB. The only problem was that on the over run the exhaust fumes come back into the car which is not too pleasant.
Over the winter I will take the original Marlin silencer to Custom Chrome for them to modify to be more efficient without reducing power then replace the small silencer I bought from them with the cat. I should then have the best of both worlds with an efficient ehaust that keeps things quiet without strangling the engine but no nastly smells. That way I will not have to bother changing cats and silencers for track use or MoT time.
There are plenty of guys on the forum with Westfields who can probably give advice specific to your car but I can certainly recomend Exhausts by Design and Custom Chrome. Locally, Infinity Exhausts are well recommended just never had the need to use them.
I used pro-speed exhausts in Cardiff, they did my cat insitu on the shelsley and I was really impressed with their quality of work (and the price!)
Chris