Well the best bang for your buck would be a muffler delete. It actually sounds good if you put a set of vibrant resonators or any resonator for that matter. Now if you have catless downpipes, secondary cat delete and muffler delete, then its going to sound way to loud and raspy. But just cutting off the muffler with the stock downpipes and secondary cats is def the best bang for your buck. it also = less restriction for the turbos.
A/W E92 335i M-sport with JB4 G5 ISO/ E40 WEDGE PERFORMANCE BACKEND FLASH, Alpina TCU flash for AT/Switch-tronic +AR Downpipes, Stett gen 1 intake, Wagner-Tuning FMIC+RB Turbo setup/ RB PCV Valve+ Akro exhaust+60% E85/93 mix,+ HRE P40S wheels, KW coilovers, M3 sways,+BMW performance CF Mirrors, BMW Performance CF deck lid spoiler,+ CF interior trim, p3 vent boost gauge,+ LUX angel eyes (11.73@119mph on street tires) NO METH!