You need to adjust the bowden cable, it controls shift timing, while vacuum controls shift quality. It's an easy adjustment on the m104 engine. With the hood open, stand at the drivers' side fender. The throttle cable is easy to find, it's below the plastic intake manifold and runs vertical, up and down. From there, look a bit toward the rear of the car - the bowden cable angles up and toward the firewall. It has a threaded plastic adjuster, and the cable itself is covered with a protective plastic sleeve. Turn the threaded adjuster by hand to slacken the cable. The specification is for no tension with the throttle in the idle position, though it's a bit difficult to tell the tension level. I suggest just slackening it 1/2 a turn, then go for a drive. Repeat until the shift points are acceptable.