to be honest, i think the smoke rob is on about is the richness of the fuel mixture on full load, mine is the same on full throttle, mine belches black through gear changes, not so much now as i've had it trimmed up for my run to france, but having a little extra as you let the throttle off helps with piston cooling on high speed runs.
by the way den, i did like that feel of the big tubby, it made me grin like fuck
i was still smiling 2 hours later, i'll have to take you a spin den, see what you think of the old 8 valve.