I asked the question a few months ago how to get rid off the questionable engine rumble more associated with off-tuned engine firing order.

Its going worse and louder now at 3.2K.

Any idea how to fix the problem? I just want a cool free flow exhaust all the time.

 

My 2012 JCW exhaust pops and cracks on upshifts--it is my understanding it is supposed to. Not sure about a timing issue though.

 

Does it only do it when pressing the Sport mode button?

 

So I am a little late to this party.... But.... In sport mode only, the fuel system delivers a little pray of extra fuel to the cylinder after you let off the throttle but does not apply ignition. What the result is, is fuel hitting the hot exhaust manifold and essentially exploding. It does not effect exhaust flow or anything, it simply sounds cool.

 

It might help the scavenging in the exhaust. Turbos don't like back pressure. It provides resistance to the hot gases exiting the turbo and adds a little to the lag. That mini-explosion forces whatever is in the exhaust system out and the pulse leaves a bit of a vacuum after the turbo.