If you use the link I provided to the Permatex Ultra Copper Silicone RTV
spec sheet, it'll tell you that it is oxygen sensor safe and that
exhaust flanges are one of the recommended uses.

Mike

Scott Daniel - Shazam wrote:
> People should always be aware that the use of silicone sealants where an
> oxygen sensor is involved is a big no-no.

> http://www.permatex.com/documents/tds/automotive/81878.pdf