A higher fuel burn multiplier has a disproportionately negative effect on short range, high altitude fighters such as the Bf109K-4, P-47M, Spitfire Mk IX and Spitfire Mk XIV because while the ranges are compressed, altitude is not compressed, nor is there a way to compress altitude.
Further, the burn modifier has little effect on long range fighters such as the A6M2, A6M3, A6M5, Mosquito Mk VI, P-47N, P-51B, P-51D and Ta152H-1 and mp effect at all on bombers. Fuel Burn 2.5X would actually further distort the speed advantage that bombers have in AH.