The Diecast Cars page should help. During the race at Darlington, Jeff's pit crew was recruited to perform a stop for Johnny Benson. Jeff's team had already dropped out of the race with engine problems. Johnny Benson's team gets chassis and engines from Hendrick Motorsports. In effect, it's a Pontiac team sponsored by Valvoline on the outside, but a Hendrick car underneath.
Any pit stop performed in an actual race situation is advantageous to a crew.
Compared to some of the other top drivers, Gordon has rarely had an on board camera during his career. The cars sponsored by Miller Lite, Budweiser, Home Depot, UPS, Phizer, and Dodge seem to have been selected from the on air cameras more often. The former pit crew left after the 1999 season. Dale Jarrett has not won any championships using the former DuPont team pit crew. As far as why they left, they made a business decision and signed a contract with Robert Yates Racing.