Can't answer your question directly but I know someone with a 2012 X5 50i and got Dinan Stage 4, Air-to-Water cooler, and the free flow exhaust. According to him the gas mileage is getting pretty close to X5M's range, and his only regret was that he should have gotten an X5M instead (considering the MPG he's getting and the money he spent on Dinan mods)