Hi guys i already used search and couldn't find anything, so here it goes. Today i got a new BPM GT 3" TBE installed at ASG. The midpipe was a bit short so they welded on a piece of extra metal to it so it all lines up perfectly, which it does and looks great. My problem is that when i drive its got that boxer rumble but when i release the throttle it makes a sort of popping sound, thats only when i release the throttle. Is that normal?

also when you drive you can hear like movement underneath, is it possible that its loose and its knocking on something because there is a knocking sound underneath the drivers side constantly when you drive, sometimes it disappears for a min or two and back it comes. Any suggestions as to what it would be? or if its normal :S