I have a 3' exhaust with no cat and no silencers in the downpipe or exhaust so its really loud. I wouldnt mind it being abit quiter ( i know strange thing to say ). Anyway to reduce the noise without loosing power? 

 

I have looked into soundproofing has anyone tried this? 

No idea about sound proofing but maybe a resonated centre section will reduce some of the noise

look at the exhaust itself as you wont soundproof windows for example, also it is a lot easier to fit and if you think it is noisy in the car your neighbours will probably have a similar opinion.

A decent quality item will not impact the performance massively - if at all.