Just recently removed my air pump and put a RB header on my car. Now it is overheating. I measured a temperature of 265 at the water pump housing. Radiator temperatures were a lot lower and I recently had the radiator dipped, boiled, etc. I do not yet have the twin sheave pulley installed. I am running without the TPS hooked up and without a O2 sensor. I am not sure if the Variable Resistor is set properly. Is the double sheave pulley pretty much mandatory if you remove the air pump so that the cooling is maintained?

 

I have had cars where the belt slipped and screeched no matter how tight I made it and the I have had cars that ran a single belt and it was fine. If you are still running a clutch fan I would say that a dual belt pulley is pretty much a necessity

 

If your radiator is known-good and you just pulled the Air Pump out, realize that you've lost some pulley tension on your waterpump, which could very well result in poor traction for the engine fan and also poor traction for rotating the waterpump - a 2-pronged attack on your cooling system!

Mazda designed the layout of the pulleys and various pumps to ensure that a balanced load was placed on the various pulleys and belts. Once you remove one of those items, it's unbalanced and the shafts of the resulting pulleys will have an angular force applied to them instead of balanced. Is there a way for you to reinstall the Air Pump until you get the double-sheave pulley installed?

I wouldn't drive it if you're overheating - the single most common factor for killing a rotary engine is overheating. Good luck,