When accellerating modestly/hardish when in Drive mode when in 5th gear, it feels like the tiptronic is downshifting to 4th gear (the rpm also goes up almost instantly with 600+ rpms). But when switching the stick to 'manual mode' then the dashboard display still shows like it should be in 5th gear. Even when in Drive-mode and no longer pushing to accelllerate further it stays going at 3000-3500 rpms without gearing up again (it also shows its already in 5th so how should it be able to? ;o)

Trouble is however that I still only drive at maybe 130km/h (80miles/h).
Model is 2.5 Tdi with 180HP from 2004.

Does this sound like an electronic problem?