POlO 1.9 sdi ASY, idles a bit higher

[tacheyo]

Hi , I have a 54 plate, 3 door polo ,1.9 sdi twist, that has been running extremely well. A few days ago i noticed that the car idles some times a bit higher at 1000 rpm. I have been keeping an eye on it and can say that the increase in rpm is not due to any of the following:
1.engine temperature(it happens when cold and also when hot).
2. i thought it may happen when the heating is on, bad the same happens when using cold air.
3. lights on or off no difference.
4. after driving 2 miles i could notice increasing and decreasing of the idle happening a few times without any pattern.
5. when waiting at the lights if i press the acceleration pedal a few times i saw the idle dropping to the usual 850-900.
Is this something to worry about? On a obd code reader, i did not shoe any errors. I am thinking about egr or throttle body that maybe needs a good clean, also the car does not vibrates just idles a little higher.
Thank you very much , and hope to hear from you soon.