Nuevo 2004 throttle issue

We have today taken our lovely “Bob” out for the first adventure from Devon to Cardiff. 
Habitation wise everything is hunky dory but the drive was “interesting”
After approx 50 miles of cruising along at 60-65mph I felt the revs and speed drop.
We pulled to the hard shoulder and in doing so things rectified and we pulled away again. 
Another 30 or so miles and the same again but this time when we pulled over the throttle suddenly stuck open and revs went crazy. Turned off and on and all fine!
No dash lights and no smoke.
Repeated another couple of times until we arrived.
Any thoughts?
Like many the Motorhome has done very few miles last couple of years and the mechanical pre purchase inspection found no problems.

Hi Wilki.. could it be something to do with the sensor under the accelerator pedal......assuming yours is a "drive by wire" rather than a throttle cable.   Sorry can't be more explicit as I don't know the technicalities of the system.    Just a thought.

And the winner was…..

MAF issue

Sorted by the garage as part of a major service and check over and tonight she flew up the dreaded Haldon Hill in 5th no problem at all