bungs with widebands and I have a 2.5" Greddy catback that I like . I wouldnt plan on running the set up that im questioning except at a track. I'd like to still be able to use my greddy catback for daily use . The Greddy exhaust I have has a 4.5" tip on the muffler but the ID of the muffler is barely over 2". So my current system start with 3" down pipes and eventually turns into a 2" outlet ,which is ok for daily use but at times Id like to open it up with out the expense of changing up my whole system . Thanx