Is anyone running a mac hi-flow cat with a 3" i-pipe?

I had midas tell me that my 3" i-pipe will not seal with the mac hi-flow cat because the ball joint is much smaller than the 3" ipipe's flange. However, when I ran a MAC offroad pipe, they sealed fine.

Is the shop giving me BS? Have you guys had the mac hiflow cat seal with your 3" ipipe perfectly? Right now I have a huge puffing exhaust leak sound from there...

 

i hate to do this, but... ttt