hope I explained possible fix in the E-mail I just now sent, will copy paste here,
This is a long shot but check your TPS and run the Reset ISCV function in TuneECU the TPS should be 0.6 and stepper motor should be 0.72.
Even if the TPS is slightly out there should never be a larger or smaller tolerance of 0.12 between the two, if after resetting the ISCV and it starts doing it again I would look at replacing the TPS, there is no given lifespan of a TPS as my original one lasted 20,000km and the second only 7,500km they are temperamental fragile ****s of things another test is to while having TuneECU connected watch the voltage on the TPS increase as you very gradually open the throttle up to the troublesome area then hold it there, if the voltage starts jumping around and the revs are a bit uneven then it is definitely the TPS ... don't ask me how I know or how long it took and how many other things I checked before discovering this, the TPS is a Rheostat and can develop a weak spot or two
Cheers Hans