Have a question For the "real" mechanics here; neighbor has a Ford Expedition he managed to rip the exhaust pipe in half & asked if I'd weld it up for him. It's a bit mangled, needs to be trimmed back to square and sleeved so here's my question; should I sleeve it on the inside or the outside? Would the wall thickness of an inside sleeve impact the back pressure enough to affect performance?

Not a huge deal just helping a neighbor but it's as easy to do either way and want to do it right for him.

Thanks guys.