I hope you don't mind if I cross over into the "1st Generation MINI" forum to ask a question. We seem to be identifying a carbon buildup problem in the 2nd generation ('07+) MINIs, and I was wondering if anything similar was going on with the earlier MINIs. Click on:

https://www.northamericanmotoring.com/forums/coupe-talk-2007/160099-excessive-carbon-build-up-in-engine-2.html

Even when only premium gas is used & all other guidelines are followed religiously, we are finding carbon buildup in the intake ports in the head. It seems to be localized (or, at least, worst) in the #4 intake. Is this peculiar to the turbos ('07+), or has it been noticed in the earlier supercharged engines, also? MINI service facilities seem reluctant to label this as a mechanical problem....prefering to blame it on "bad gas" (& therefore a customer-caused problem) even though gas receipts prove otherwise.

 

Sorry.....For some reason my link (above) doesn't seem to be clickable. But, if you go to "2nd Generation MINIs" in the Forums & click on "Coupe Talk", then "Excessive carbon build-up in engine", you'll be there.

HHH