I was experiencing the exact same problems.
I took out the idle control valve. Cleaned it thoroughly with brake cleaner. Spray the inside (thru holes), let it sit for a while, shake it and repeat the procedure until the liquid comes out clean. Then I sprayed some WD-40 to lubricate the moving valve inside, shake it well.
I also cleaned the trottle body bore, as Kestas suggests here.
I have not had any stallings since then.
This worked for me.
Just my 2 cents.
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car