Exhaust manifold is not cracked and no leaks, doing a process of elimination, valve clearance check, engine has had a rebuild, carby rebuild, Exhaust pipes ok , going by previous comments I will change the muffler, yet another tune, tyres ,bias, are new, at the moment thecold girl sounds like it has wind pain.
It is good to know these vehicles are to proceed quietly down the road and thankyou for the supplied information