I have headers that have ports on them right at the exhaust port for air pump lines to go in. I haven't had an air pump for many years and have some plugs in those ports. I'm concerned they may be leaking a little and messing up my oxygen sensor readings. I used permatex ultra copper before and it's totally wasted. I'm in the process of redoing it, but I noticed the stuff is only rated to 700 degrees. This is the absolute hottest part of the exhaust system and surely gets hotter than that. Does anyone have a product they recommend to seal at HIGH temp?

I guess an alternative would be to get better plugs. Right now I just have some things from the plumbing aisle that seemed to fit the threads, they don't really snug up. Anyone happen to know what air pump lines are? Maybe NPT?