Best cleaner for lead exhaust residue?

"I have a 915iS ................"

Hmm! There has been conversation, on this Forum, involving fuel injected Rotax and inflight fuel vaporisation (FV). I have no experince of such engines but understand that they have more fuel pumps and necessarily higher fuel pressures, than their naturally aspirated relatives, all of which may exacerbate FV potential .

In my experince of FV is primarily a ground based phenomena, on especially hot days, after running the engine and re starting before engine (& fuel lines) have cooled to near ambient.

In Australia, I have not heard of a naturally aspirated Rotax 9  having an inlight FV problem.

Improved technology often comes with its own peculiar problems 😈

I never had an issue with ethanol fuel either in my Flight Design CTSW up to 12K. I guess under the right circumstances it can happen, but I've never had an issue and no one I personally know has. But as they say better safe than sorry.