I honestly feel that's clutching at straws, but if it does indeed turn out to be the cause then great.
There was a episode of fith gear where they tested the top brand juices and surprisingly Bp was the worst performing out of the top branded fuels, shell v power nitro came top.
From worst to best there was 5bhp difference in a golf gti so yes fuel is different, but is it bad enough to cause to problems you have had not so sure
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