The off road pipe is not meant to bolt onto an exhaust unless you fab a 3" system.
Bolting a 3" -> 2.5" would kill your flow. That was the point I was trying to make... I hope I was clear?
If you want something for daily street use, etc, I was recommending the high flow cat as that would let you use stock or afgtermarket exhaust systems.
Thanks for the help MrQuija