pretty much what Hahns said you gotta fiddle with it and tighten one bolt a little then the other one a little back and forth. Make sure its seated properly cause I thought mine was good and it was a tad off and made it leak

 

Come to find out. After we took the header on the right side (since it seemed it was leaking most) it seated into the pipe just fine! But my buddy forgot to tighten the last 2 bolts closest to the cab : / so we destroyed the gasket getting the header back off so I had to buy more. Going to hopefully get it all together tomorrow.