Engine problems when warmed up?

[Fad3.In]

Hm,I m not sure how to put this... :-/
My car behaves in a different manner when fully warm up.
The engine gets somehow slower to react to the gas pedal from idle.
There s a small but noticable lag when revving it.
When the car is cold this doesnt happen.
Also when warm,there s a bigger chance I ll hear petrol knocks
at around 3000rpm,something that never happens when the engine is cold.
So,apart from changing petrol station what else shοuld I check?
Apart from that I think my clutch fan needs to be replaced.
It may be hot here,but I ve never again seen my temp gauge go over
to the third mark(line) before in 4 years.Now it sometimes gets there,
even though it goes back in the middle soon after that...still,I wonder.
The noise the fan makes is also louder than before,so what do you think?
Thanks for all you comments/suggestions,tips... :-)
N.

PS.Apart from all these,the car is fine...Acceleration is fine and there s no throttle lag in higher rpms!

[Fad3.In]

Noone knows anything about this?
I must add that I also messed with the mixture screw in my AFM.
In fact i turned it counter clock wise 1/3 of a turn just to give my M10
a bit more air,cos it was pinging a lot under acceleration some days ago...
Thats was wrong or just ok?
N.

[James]

Have you checked your thermostat? Your fan could be fine, but thermostat is broken.

In regards to your tuning issue, I don't have any suggestions.

[Fad3.In]

Originally Posted by James

Have you checked your thermostat? Your fan could be fine, but thermostat is broken.

James,how can the broken thermostat cause the problems?
Can you elaborate please? : )
N.

[bmwfreak e21/30]

Do you have an open air filter ? if so the hot air from your engine could be the problem .
goodluck with it