So I want to buy these https://www.summitracing.com/parts/p...model/trans-am

Will the Y pipe they sell bolt/weld/clamp up to my Borla catback system? I feel like the answer is not easily...this is what I had.

 

My 97 DD has pacesetter LTs and a Borla catback. I just had an exhaust shop make me a y-pipe. It cost less than the aftermarket one.

 

If you can find an exhaust shop that can make you an off-road pipe, then go that route. That way fitment will be guaranteed. The pre-fabbed ones (any brand) have been known not to fit well and grinding/hammer needed to be used to make them fit.