i have never used any sealant, however, i have used a thin layer of grease.
remember there are 3 gaskets..i have seen the thicker cork one(inside) get left out and it will seep out the end (thin fiber gasket)...tightening won't help.
Thanks for all the replies.. I installed the adapter with no sealant.. I did have to loosen the header all the way to get in though. definitely a two man job..
HKeller
yeah its not fun trying to hold the gasket in place and not let the bolt drop while your trying to move it in place around the header by yourself like i did.