Its actually not a good idea to just remove the resonator if you arent pushing more air through the car. The car is currently tuned for as close to perfection as possible by the BMW engineers. You need some back pressure when your exhuast and intake valves are open to keep the cylinder temps hot so that they dont cool down and slow down air movement through the cylinder. If you arent pushing more air through than before, having a less constricted exit on the exhuast doesnt help. It actually creates turbulance, usually found in the exhuast manifold that hinders the flow and as a result creates more back pressure than with the resonator.
But I think in both situations, it wouldn't be noticed on the butt dyno.
06' BMW 330i & 03' Suzuki GSX-R600
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