RPM's wont drop between shifts

[hancock]

I tried searching and came up empty but I am running out of ideas..
The car is a 2001 VU Ute
When I disengage the clutch to shift up a gear the RPM's wont go down until I shift or they will take 3 or so seconds before dropping.

Ex: Shift from 2nd to 3rd at 3000rpm: I let off the gas and push the clutch in, the rpm's will go up to 3200ish then back down to 3000rpm and it will stay there until I let the clutch out.

what would be cause this?

any help would be apprecatied.

cheers

[v6lux]

Sticky throttle body??? Return spring missing????

Does it have a cable or is it "Fly by Wire"?

ECU in limp mode??????

Engine ECU temp sensor fail????????

Have you done an error code check?