Hi Bobster.

My 2009 Sigma has covered 92,000 now and regularly runs on supermarket petrol scared with a fill up on Shell Nitro 1 in 4 fills. I get a bit of burbling on overrun sometimes (which I enjoy). I change gear at 2,500 to 3000 revs but occasionally allow her to go to 5,500 in 3rd if a Yaris wants to show me how quick it isn't innocent .

This doesn't help your problem I know, but I suggest it's NOT a fuel quality issue.

Cheers

Jeremy

2009 4/4 Sport Green

And nothing else !