My Mrs just had a upgrade. She found MIJ Performance in Walsall to be the best, as unlike most there boxs r not pre made. Giving u a full custom exhaust.
We looked around and didnt find anyone else that offered this sort of service.
What we were told is that Milltek, Longlife, and so on there boxs (silencer's) r premade across the water. So not 100% custom exhaust.
Still great exhausts tho come along to the meet this weekend, u will be able to hear to lots of different exhausts.
Judge yourself
sound differents? yer def sound differents and also the more u have done the more the sound changes.
Power gains? again depends how much u have done. if u have full exhaust with sport cats, im sure u will tell differents.
Remap? think its optional but could be wrong, sure someone will come along and say.
free flow? xpipe seems the way on here
Quad pipes? fair few r getting them from MIJ