oil guage / pressure problem

Hello everyone,

I have a 1990 500SL with 73000 pampered miles. The car is in excellent condition inside out. The only problem is: Once the car gets hot, the oil pressure guage will drop and the red light will come on when excellerating. Once I take my foot off of the gas, the pressure will return and the light will go off. I do not hear any engine noises while this is happening and the oil level is fine. I appreciate any help anyone could provide.