hi Mike. I've had no major issues running 91 octane in my L46 with 36* of total timing and I've run it pretty hard. Sometimes on hot days it'll start to ping up near redline, but nothing that's really concerned me. Having said that, I'm sure that your results may vary depending on the condition of your engine. The more wear and tear on the rings and valves the less of that 11:1 compression is being taken advantage of. So if yours is pretty fresh compared to mine then you may have more issues.