UHZT

I have a Protege Y2K 1.6L. When i have my head lights on or my A/C on, sometimes when i stop at the traffic lights my idle goes down to 400-500 RPMs once or twice and then stabilizes in 750.
I have tried everything but the problem is still alive.
I use to clean the intake butterfly valve, i spread carby cleaner in the bypass holes of the IAC valve an spry some cleaner in the passage of the idle adjust screw.
After the cleaning, the oscilations in my idle speed almost dissapear but when i am abouth to stop the car shows an idle of 1100RPM and when it stpos completely drops to 850. in other words it remains accelerated. as i run the car , the idle speed begins to drop until it reaches normal values 750RPM (in about 5 days) and a few days after, these oscilations begins. Why is this happening? what could be changing temporarily when i clean the elements mentioned?

Regards
UHZT
Y2K Protege 1.6L
K&N drop in air filter
Custom side sills kit
Flying in the caribean...
900 Watts, audio power