VY Commodore Revs dropping when cruising.

[Cadbury Commodore]

Hey Everyone,
I have a VY Commodore executive wagon, auto...
When I drive at a cruise speed, normally anything on 60 km and above, and particularly at 100-105 kmh, the revs drop by about 500 rpm, and then restore.
It happens several times a minute, and is particularly noticable when going uphill. Mechanics are a little mystified as they thought it could be the knock sensor, but it's just not pulling back hard enough with the power, although it goes back 500 rpm, it's a very minor power loss. It's kinda surging but without throwing the car around, I'd barely notice, in fact, the first time I drove it I thought it was just the wind on an open freeway, but it happens all the time.
Does anyone know what it could be? Any ideas?

[malik]

ill tell u how...... say u set the cruise control at a speed of 90 kms....so the computer automatically keeps in mind and makes sure that it has to pull up to the speed which is what its been designed for..but while down hill this wount work... hope this helps... because the cruise control keeps the car the designated speed so it has to pull up a bit... well this is what my concern was but i figured out.....

[Cadbury Commodore]

Malik,
thanks but this wasn't my problem. I don't have cruise control.
It turned out to be the knocking sensor, although it didn't look like it was, it was, just needed it to be less sensitive and now it works again!
Thanks for your help.