I have a 2002 YZ426 used mainly for trail riding at altitudes from 1,000 - 5,000 feet. At the higher altitudes I get a significant performance drop-off including poor low-end throttle response. I'm thinking that the Boysen Quick Shot would help with that but I know that the jetting needs to addressed also...should I go with the JD Jetting? Also, some of the single tracks get pretty slow, steep and rocky requiring lots of clutch work in 1st gear so I'm going to gear down a little bit, but I sometimes get concerned with overheating although I haven't lost any coolant...is Engine Ice recommended? Interestingly enough, no matter the elevation I have zero problems with hot or cold starting. I'd appreciate any tips...thanks!