I have a 99 mach Z. Last weeks drive it worked just like it should.After sitting a week it was more hard to start than normal and after a brief warm up took it out for a a short spin on a straight with some new snow.Shortly started to run on 1 to 2 cylinders. Checked and installed different plugs,no difference.Suspected water in fuel. Disassembled carb and checked, found some condensation, reassembled, started and run just fine.Took for another drive and now cannot get rpm to go over 7500.If you feed it slow while driving it pulls hard up to approx 7500 and when pressing throttle full, rpm falls back and feels like its bogging.Certainly feels like carburetion.Had local dealer check carbs again,cleaned clutches, check rave valves,drain tank and check fuel filter, all okay.Compression okay. Have any of you experienced such a thing, or what do any of you think might be the problem. It certainly does not feel like fire as there is no miss, and engine starts fine and seems to haul okay until the higher RPM.