The RAF was using 150 octane as well, so if your question is about allied fighters the RAF figures have to be added, if Europe you need to add the operations of the allied forces in the Mediterranean, which stayed with 100 Octane. If it is US in the ETO fighters that has the issue the 8th and 9th were fighting different battles and the 8th was more likely to encounter Luftwaffe fighters, so it is not a number of fighters or sorties, probably the best measure is the number of claims made by the fighters. Plus knowing the dates the US fighter groups switched to 150 octane and noting the F-6 reconnaissance units were armed and making clams, one of the 9th's fighter groups became a reconnaissance group.
The higher octane fuels gave better low level performance, they did not give any better high altitude performance. To illustrate, the Spitfire VIII modified to 150 Octane and 25 pounds boost, versus its 100 Octane 18 pounds standard configuration, was 30 mph faster at 14,000 feet but no faster at 20,200 feet.
Just post war the USAAF put together summaries of operations, any RAF ones are harder to find. The attached are when the 8th was using 150 octane, the relative fighter strengths of the 8th and 9th and their claims which can give an idea of the ratio of 150 versus 100 Octane using USAAF ETO fighters encountering Luftwaffe aircraft, the overwhelming majority of USAAF claims in the ETO were for Luftwaffe fighters.