328i remap

hi, new to site, just done m50 manifold on my manual 328i convertible noticed improvement on top of rev range, slightl loss of torque on early range (less than £3k revs) but happy with mod would like to do remap to up bhp and also stainless exhaust but dont want noisy exhaust, any recommendations re exhaust & remap?
Regards neil
Regards neil