I'm looking for some assistance as the Sea-Doo web sites I've been to have been useless for help and I know everyone here is pretty good. I've got a 2002 Sea-Doo GTX RFI (800 SDI) for 3 years now and this is the first time this has happened. As far as I know, except for displacement, it's the identical setup to the 600 SDI on our sleds. It starts right away every time, hot or cold. Idles smooth. Never stalls. Runs smooth above 4000rpm and hits an indicated 100kmh. My problem is that between 1500-3800 there is a pronounced miss and a stumble if I hit the gas gentle. No problem if I just pin it. The plugs are new. Thanks in advance for your advice!!!