I have installed a new exhaust on my 91 z28, new stock exhaust manifolds and stock y pipe that go into a new 3" magnaflow cat and a 3" hooker exhaust from the cat back. I however can't seem to get the y pipe on the passenger side to seat properly into the donut on the exhaust manifold. It's driving me nuts. Any way to fix the problem? Should I replace the y pipe?