3 Questions: High RPM at start up & oil coming out of pipe '98 670X & jetting

1. Your pilot circuit might be a little lean. Try screwing the air screw in 1/2-1 turn.
2. First check your oil cable make sure it is not hanging up, check the linkage, make sure the marks line up.
3. The DPM takes care of most of it, however, with any new to you sled purchase. It would be prudent to check the jetting. Maybe check the pilot jet while you are in there, it could also be related to the high idle.

I owned a '98x at one time. This particular sled would do that as well. Start it cold - high idle RPM. Once it started to warm up - it would drop down to a normal idle. I attributed this as to a function of the DPM. Funny thing though, the stator burned out, and after replacing the stator, it quit doing this.

About the oil.... It is not uncommon for 670 oil pump check-valves to leak over the summer. If you have a full oil tank, it is possible for the crankcase to fill with quite a bit of oil. It is possible that this is what happened to you. I would think, that after a short ride, that the oil that has been blown into the pipe from the 'case will burn out or blow out with the exhaust.

As for jetting, 'Doo jetted them for sea-level conditions, which means RICH. The DPM leans the system from there as needed, dependant on temps and or altitude. I leaned my own 98x down one size on the jetting to crispen it up. Going from 3000 to 5500' of altitude, I would not really worry about the stock jetting.