Sounds like there's a vacuum leak, the modulator valve needs to be adjusted and if what you mean by the "rear bank" is at the back of the cylinder head just above the bell housing then it sounds like the head gasket is bad. Is there any oil in the coolant or vice-versa?

A vacuum leak can cause both rough shifting and a rough idle

__________________
89 300te 222,222
92 300e 190,000