I torqued the CAT input / output flange fasteners according to the manual 32 ft-lbs, but I noticed the flanges looked so squeezed together that the flanges were bending. Sort of imagine claping the ends extremely tight but in the middle it was NOT sandwiched as tight as the ends. Sort of bulging in the middle, but sqeezing on the ends.

I'm wondering if the seal is not uniform. These flanges are not the 3 stud type like the header pipe to exhaust manifold flanges, These flanges only have 2 studs on either side.

I was considering just snugging the flanges so the gasket was snug, but to the point where the flanges wouldn't bend...but I just ended up following the FSM, instead of guessing.

 

Sounds like you have a cat with floating flanges instead of welded on flanges....with their thin construction ya they'll bend!