Hi, I had a DRZ400S before my XT660X, as for the fueling / surging issue mine has a little, but no worse than the DRZ, but over a smaller rev range, hot enough to warrent anything NEEDING to be doing to it, but I'll never say say never LOL. The XT was the perfect upgrade for me, a little more power, a little more speed for motorways etc and a little more comfort, the list of "a little bit more ---" goes on, oh yes the bad bits a little more to tax & insure. The DRZ is a fantastic little bike with no complaints at all and I was a little unsure about changing it, but the XT is just as nice and I'm loving it, all the above posts really do say all you need to know, hope you make the change, Mike