I see the warp mine was the same around and inch top to bottom [worried me that when I tightened it down it would crack]. My problem was two fold my inlet/outlet placement and application I could not find what I wanted in a better brand in my price range. I apologize for being rude! I knew going into my selection I would be modifying it but that's what hot rodding is all about.
My guess is that the fixture [jig] they use to weld them up is either crooked or not clamped correctly or not enough cool down time after welding.
