Hi had this problem on my 2003 plus 8 while in holland last month thought the throttle cable or body was sticking. Brian Miller was on hand and gave this advice which worked.
Due to starting the car from cold and pulling away without letting the engine come of cold start mode, the ecu has a funny and will not settle the engine to idle.
Always let the engine idle a little while before pulling away.
This was Brian's advice has his plus 8 does the same.
regards
Phil