I had a local company in Ipswich called Demand Engineering/Longlife Ipswich add some pipework and a rear silencer to the already excellent Powerspeed system I had, as well as repack the Powerspeed silencer using their materials and techniques. Powerspeed 24" x7" side silencer by itself was 97dB, with Acousta-Fil Boa inside 94dB and now with the DE-repacked Powerspeed silencer and rear silencer it is 89dB, all at just over 5000rpm on a 230bhp 1.9K. I found that static tests were never a problem with the Powerspeed system alone. Just when barely thinking about using the loud pedal, I got chucked off the circuits. Cost was an incredibly reasonable £300 for a morning's work. Here's my trackday heap: http://www.mankee.plus.com/DemandEng.jpg PS. Demand Engineering did the manifolds and exhaust system for Guy Martin's Transit van in the latest Speed series. I tell everyone this because I'm proud of the top-notch local companies in East Anglia that appeared in the programme.