I love a little deceleration pop on my 20 iron 1200. Neighbor haters doing their thing.

 

I was just fighting the same issue, rear pipe exhaust flange nuts would come loose every 10 miles.
I finally loosened the whole pipe, realigned & retightened every nut/bolt starting at the head and going down the pipe. Seems to be holding now...

 

MXJunky isn't sure about cruisers but on a dirt bike when you remount the exhaust, after mounting the header and silencer you want to start with tightening the silencer mount bolts first and then put the final tightening on the headers. (You basically mount them but don't fully tighten the fasteners until each piece has been placed and tighten from the rear forward.) It would make sense if this was the case for cruisers and could be contributing to exhaust leaks, et cetera.