chrispynuts

Hi can any one advise , my ml270 has the egr and the manifold mods done plus a new maf and map sensors replaced .When accelerating hard i.e. foot to the floor and pushing the kick down switch the engine revs to 3500 then hesitates as if the engine has been quickly switched off and back on again then revs on up to 4500, before changing up a gear BUT will not change any further and seems to be stuck in gear and the revs have to be kept up and slowly let down then the gears change. Could it be the electric plate thingy inside the gearbox starting to fail. any suggestions please !