Can someone explain this to me?
 

Why is it after intake and exhaust mods are done to an Rx7 these cars run hot (hot coolant temps)?? I figured with increased air flow thru motor they would run cooler?

What's happening is your engine is using the extra air to burn more fuel. More air and fuel = more energy = more heat. Do the fan mod or get an aftermarket radiator to help keep your temps down.

get an aftermarket radiaotor no matter what, and dont forget to get the an aluminum ast while u are at it.

Thanks for helping explain that to me. What does the AST do? I was thinking of just getting the bypass and not an aluminum AST.

ast gets rid of air bubbles

More Horsepower=More Heat, it is a basic law of physics called the Law of Thermodynamics. Increase one side of the equation(just like chemistry) It must be a balanced equation and thus more in means more out-Just like Jonski said.
Art

Just scrap the AST. I know several heavily modded and nearly stock FD's that have removed their AST and have no problems what so ever. Mine is coming off when I get home from this deployment. Best of luck.

Zach

I personally didn't notice any cooling differences between the AST being on or off. On top of that it costs more to get a aftermarket AST and it saves space to have it by-passed.

Garrett

ast gets rid of air bubles period, the whenever a radiator sits as low as it does in an fd u need an AST. its not something that only mazda uses, and there is apurpose for it. some heavily modified cars have teh radiaotrs inteh upright position thus not needign teh ast. you can obvisouly run without one but in my eyes it would be less reliable to do so, because it would case "more" of teh localized boiling which is when yu have air pockets in teh cooling system and when next to the parts that have to get cooled down such as teh engine it will not do the jop since air doesnt conduct heat as well as water and therefore damaging teh coolant seals

hope that answer your quastions