Having issues with installing the muffler/exhaust header on my GTR: Seems the headers will not slip all the way into the head when the end of the header is seated in the rubber gasket at the muffler/header joint. Is the header supposed to butt up against the muffler inside the rubber gasket , or is their supposed to be a slight gap? Also, the muffler/header gasket has a raised lip inside, and I assume the entrance to the muffler butts up against it; doesn't make sense for the header to butt up against the lip. I've tried to install the header and muffler loosely so that I have room to make sure everything lines up, to no avail. So what am I doing wrong? These are stock mufflers and head pipes, BTW. Thanks in advance.