Just checking to see if you solved your Jerky issue. I have a 2001 H6 with the same issues. It triggered a chk engine light with a P0122 code "throttle possition error, low voltage"
There appears to be other posts on this subject and a subaru survice bulletin dated 11/08/06.
Does anyone have any experience with this or have the service manual pages for throttle possition sensor replacement?