Found another source on the 2nd TAF use of 150 octane, before you say "oh please no", hang on. It indicates early Feb 45 for 126 Wing (RCAF)(Invasions Without Tears, by Monty Berger), so again, I think a +25 lb XVIE would have been a mistake. It did use it to be sure...but only in the last 4 months of the war, and at some point game balance and a degree of "what was the most common" does come into play. If it only ever used 150 then I could see making a case for it...
Personally I think its a dream at +18 lbs performance. Perhaps the best dogfighter in AH now, with air ground ord to boot.