Late last year I lashed out on a set of G56 exhausts, after hearing one in the flesh and reading the excellent reports they receive.
Not cheap but at that price I was expecting faultless performance...
I associate "faultless performance" with Toyotas not Morgans

Is this more a rattle? If its an exhaust valve noise it would be at rpm/2 so at idle 1200 rpm = 10 taps a second...