Darkfire is very correct!!! alot of poor tunes and overheating have been traced to the gasket being torn or just simply not installed right!!!

Darkfire,, if you are still having trouble getting that pig on, Try this..

1. Be very sure the header nipple on the engine is very clean and dry(Clean it with Brake Cleaner)
2. put a Few Dabs Of CA in the groove around the nipple and slide the gasket on and use a rubber band right over the gasket over the groove, let it set up.
4. Now slather mineral oil around the outside of the gasket, dont be shy here..
5. with just the header in your hand tilt the header down parallel to the chassis. With the header flange on the slick gasket adn in one motion tilt the header up and in against the nipple on the engine. with the Mineral Oil and the gasket being stuck on with CA it should slip right on.

Hope that helps!! Let me know how it goes...