IIRC my SHO Shop Y pipe is in 4 (maybe 3 I forget)pieces. The front pipe, the rear cylinder pipe, the cat, and (IIRC) a stub pipe from the cat to the remining exhaust. The Cat is a two pipe in, one pipe out (it merges the flow internally).
The "Off road" system replaces the cat with another section of pipe that accomplishes the merge. It should be 'convertable' from one to the other.
In any case, the power gain was significant in low to mid-range with some (smaller) upper-end gains. Yes I have a superchip as well and agree the combo chip, Y, and cat-back make a good improvement in both power and sound. Hope this helps.
