Update, I am beginning to notice a trend ....

I never normally fill the fuel tank up, I put in about 30 - 35 quids worth as I need it.

When I put the BG 44K in I had to fill the tank right up to get the right mix. I don't do many miles so after a good few journeys it did not put a foot wrong. After about half a tank you seem to get a bit of a flat spot and as the tank seems to empty the symptoms get worse.

I have then filled right back up again, no problems going like a dream, I am now at about half a tank and now just starting to see the symptoms begin to return in a mld form.

I am kind of hoping to see it get worse as the fuel tank empties. It is not good that it is broken but at least I can get to the bottom of what the fault is.

Fuel pump perhaps .... (stroking chin) ?