Harvey ? According to the Rotax 912 Illustrated Parts Catalog (which in addition to parts breakdowns, shows areas were special lubricants or sealants are to be applied along with non-typical torque values) section 78-10-00 page 2 shows there is no call out for the use of ant-seize compound where the header pipes attach to the exhaust port ? anti-seize compound is only called for where the ball joint on the header pipe interfaces with the muffler.
Also, believe I read somewhere that the high temperature anti-seize paste used should be copper free because the copper can have undesirable affects on the stainless steel. Unfortunately, I can?t put my mouse on that to state a source? but others more knowledgeable than I may want to jump in and correct me on that.
I think the Permatex product Bill showed is what I?m leaning towards using.