polo mk5 Gti

Hey Guys own a polo 6n2 1.6 Gti 16v what a nice polo to drive smooth shame about weak gearboxs as mines on way out aye lol but thats a different kettle of fish,

Just wondered if anyone who owns one of these have came across a issue when driving it somtimes goes into like a funny mode cuts out then you restart it and it slowly revs up when driving but only goes to like 5000revs and sounds like it bouncing of a rev limiter :S.

If i switch it off lock it for like a min or two and restart the car boom aways your uncle revs nicely like a gti should and has the performance power back behind the wheel I'm so confused what it could be i have plugged it into a snap on computer and no codes have came up :s

Much help of ideas would be great cheers guys