[michaelovitch]

I didn't read your complain well enough.
My bad.
No egr related.
Otherwise you would have problems when rpm rise,not the opposite.

It must be in the pump.
Somebody maybe added some fuel,the idle is screwed a bit because of that.

The idle rpm is regulated by a centrifugal regulator,with few little levers inside the pump,and a spring countering the centrifugal force.