The BMW M4 Coupe in its ultimate CSL guise has already garnered some criticism from European owners for its lackluster sound compared to the U.S. version. This is largely due to the particle filter mandatory in the EU. However, even the U.S. car could use an acoustic overhaul, as this video clearly demonstrates.
The owner of the car handed it over to Valvetronic Designs for the job. The tuner replaced the midpipe section with a single large-diameter pipe designed specifically for the M4. You can hear it crackle and pop somewhat distractingly in idle, but once the engine gets a load to work with, the soundtrack becomes juicy and powerful – just like one would expect from a CSL vehicle.
The stock exhaust system is partly made of titanium alloy and boasts high characteristics straight from the factory, which is probably why Valvetronic settled for replacing the midpipe alone.