Ahh this is interesting!
I too have a single, centre exit stainless RC40 and have been noticing an increase in fumes since fitting it during my resto. I'm pretty sure the joints are all good and the manifolds are tight and undamaged. The boot seal is new but is the harder type so I was thinking of changing that but reading the other comments about centre exits makes me think it could be that.
I've noticed you can alter the fume levels depending on which sliding windows you have open, so that must be affecting the flow of air into and around the car.
Good idea to try an extension on the tail pipe. I notice from period pics of the works cars that they seem to have a very long centre pipe, so maybe that's the trick?
Anyone else with a smelly centre exit!?
