There aren't any gains aside from a less muted (and by less muted, you actually get one) exhaust note. Also, the removal of the DPF increases exhaust pressure, and that has to be accounted for.
'09 E93 DCT M3 - Jerez on Ext Blk Nov w/Carbon Leather Trim
Custom Tune, OEM Perf Mod, MS Stg 2 Intake, GTS DCT/Euro MDM - MR Hood Vents/sidemarkers, H8 160, tinted tails, Gloss black kidneys w/metallic M fins, V1
WTB: E93 LCI Tails w/harness - Driver heated mirror - Exhaust tips - Driver Door Panel