Weard Heat problem

[vitali9999]

OK well heres the deal i got over heating problem in my nissan 240sx.
I have replaced thermostat water pump and radiator also filed up the colant the proper way bleeding all the air out. I cant find any water leaks so by the looks of it the pressure in the radiator is good. When i drive and shift at aroudn 2500-3000 rpm the car is staing in heat range, but if i push it a litle more 4500-5000 rpm shifts it will start to over heat .

I have tryed every treak i know yet nothing seems to fix the problem any ideas what else can cause this.