I had the same founding.

the little hole was dirty and after cleaning has given a much bettre idle at warm.

I am wondering if the flap is correctly adjusted in zero position.

Should the hole 1 be above the flap or somehow in between as on the picture?
My guess is that the hole @1 has to be above the flap and as I do not have the CD so I expect to get advice from anybody who may know

Can anybody tell what is the procedure for adjusting the flap at idle?

The hole @1 goes to the thermovalve via vacuum line

The 2 holes @2 are in fact connected inside the throttle body and act as one, they go to the regeneration valve via vacuum line on the front left fender.

I have posted some picture on the topic
"260E 1988 Euro Throttle adjustement HELP"
http://www.peachparts.com/shopforum/showthread.php?s