Is your rear muffler straight thru? I have two mufflers - rear one has an S bend in it to help keep down noise, but have set it up so I can take off the rear one at track for less back pressure. If both are straight thru, prolly not much power advantage removing either, (but will sound heaps good) - that is if mid one is like a hot dog, apparently, if it's really big, turbulence may be removed if you take if off and there will be more power there.