Last night we were going uphill in some heavy snow and the car started bucking and hesitasting. The RPM's dropped to about 600 then shot back up to 2000. This continued for about 30 in an uphill area and stopped once we hit level ground. Any ideas? No engine code. Slight smell of gas afterwards.

 

Sounds to me like you were losing traction, the wheels were spinning, and the transmission upshifted. My guess is that this is totally normal.

BTW - all the W setting does, atleast in my XC90 and 960 wagon, is start you off in 2nd gear rather than 1st. It will still upshift when appropriate.