No ... Tiptronic ... It not slipping it's something to do with the engine possibly a sensor ... goes up say from 2500 to 2600 or whatever steady speed you doing ...
Best guess would be tank vent fault or air leak but to be honest i could probably list a lot of possible items , need to see if any fault codes are listed and actual values for fuel trim really.
Only a couple of things have affected engine speed, caused it to go and and down with no pedal input from me, with my 2002 Boxster (5-speed). AOS failing and a bad VarioCam solenoid/actuator.
