Yes, your problem is in the adjustment of the control pressure cable ("bowden cable").
You are going to have to change the length of one piece of linkage about an 1/8in., probably.
With the air filter off, look down between the fuel distributor and the firewall. Move the throttle (engine off)and look for the cable (it will have an accordian shapped rubber boot where it comes from its housing). The adjustment is in a rod that pulls the lever that the cable is attached to. There will be a 7mm wrench size screw pinching the sliding link to a fixed position. Loosen the screw and shorten the link. It will be in proper adjustment when the cable starts moving when the throttle does. Don't be fooled by linkage movement. The key is the throttle and the cable (and the slack of the cable isn't apparent - hinden by the boot - take it loose and felt the spring tention of the cable). OR just shorten it too taste. Beware; all your shifts will be later, probably a good thing. If you were only getting kickdown downshifts you probably are shifting too early for good power all the time.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician