smart51
Established member
An addendum to this discussion to finish it off. I replaced the exhaust today after a piece of the old one fell off. Looking at the pattern of rust around the breaks, it seems that the weld between the header pipe and the can has been failing for a while now. With a new exhaust fitted, all remaining traces of vibration have gone away. The car is transformed. It seems that the exhaust was causing vibration and the engine mount was transmitting it to the body. With both fixed, the problem is cured.