That DOES sound a bit like O2 sensors giving incorrect information after they've reached operating temperature, doesn't it?
I'd certainly try a different dealer.
Please complete the information in your
User Profile too, to help Bill. You need to add your HEX code, the Gryphon model number and Serial Number. This DOES NOT sound like a Gryphon issue, of course, but that information could be useful someday.
- Jack