So I went with flo pro's 4" with a muffler delete pipe on my e99 yesterday and I swear the the cab noise is louder than before. I can hear the ticking of the diesel engine right where the turbo/downpipe is. I'm pretty Dan sure it's not an exhaust leak I check well.. Maybe the thinner pipe for the new exhaust? I did notice the new DP is touching the fire wall. Could it be vibrating the engine sounds into the cab? It's not terribly loud I can just hear a difference in the cab. Anyone else heard of this?