If you go from RB 6 or 7, to an odonell 77, the odonell plug is.much hotter than what you have been using, the RB 6 is hotter than the RB 7. I would think the hotter the engine is getting, the more chance of an air leak, heat expands metal, which means it opens up areas, that may be sealing well when cool, or cold. What are your outside temps in Germany now? Also the humidity?