The difference between 7.5L/100Km and 5L/100Km is A LOT - 50% worse!!

I see you've checked a number of engine/intake components, but have you checked other more simple things like whether the brakes are binding or if there's and actual fuel leak somewhere?

Not sure how the mechanic managed to "trim" the fuelling unless you've got a Power commander fitted?

Are you working out the economy with the trip meter and measuring the fuel you actually put in, or are you just going on when the low fuel light turns on? The fuel level lights/gauges on XTs are not known for there accuracy or consistency!

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