i have ipd's cat back exhaust with a square tip (instead of round). it was so expensive i decided to put it in myself. the old factory exhaust was one-piece (and heavy) and had these two prongs near the rear where the rubber bushing holds it in place. took a while but i was able to wiggle the old one out past the left rear shock.
only problem i had after installing was not being able to get it straight, the tip is a little off centered out back, and there is this slight leak in one of the joints that i couldn't fix...only hear it when cold, phh, phh. these two are problems are probably if one is fixed, other would be ok. oh well, that's what happens when i installed it myself, saved me some money to help offset that expensive price.