Well, sort of.
He made it faster, and put new tyres on.
Just looking on their website for a nose about, and I saw they do a "while you wait" service, and I thought that, as the oil is as black as soot, it would be a good excuse to look at the bikes they have and get a feel for what they're like.
Last chap didn't actually sort out my low rev spluttering, his answer was to ride it faster, which is a crap thing for a mechanic of his experience to say.
Anyhoo, I've pretty much sorted it myself, but need a couple more rides to confirm whether it's back pressure from the new "quiet" baffles, or whether it was the SeaFoam.
I'm doing my front calipers this week, and on Tuesday 7th, I'm going to Newport near Saffron Waldon for some kind of bike meet.