On the cat-back systems were it bolts tho the cat, the TTA looks to be like a rounded tapered flange. I was looking at cat back systems (bolt in) & some intermediate pipes don't have that flange, just a slip fit & clamp. If you order a system, how do you know what pipe your going to get to bolt it, or would the connection to the cat have to be welded? Anybody run into this before?