exhaust up grade

[Flattley]

ive got a 1.0l facelift mkIV, and want to upgrade my exhaust to make it sound lessw like a 'hair drier'.
i dont want it to big though.
i know that if you increase the diameter you have to shorten the pipe becuase it can cause problems in exhaust gas flow,
just wondered if any1 knew anywhere that sells them

cheers