I have a non-turbo 87 FC... I was curious what size injectors any of you use or what size you would recomend. Also, is there some sort of tuning that is needed to be done to the ECU? If so... how would I do this?

 

Why would you want to change injectors for? The ones the RX came with are absolutely fine unless you start modifying intake/exhaust and port the engine. And that's with major mods before you need bigger injectors.
Just a word of caution, If you ask questions such as this without being specific about your intentions and mods, It might invite a lot of unwanted attention from those who would jump on your case.

 

Hmm... I would have stated what mods I have... but I have none. I was just thinking that a better fuel system would equal more power. I am sort of new at this and was just looking for some answers.

 

Sorry, more fuel does NOT equal more power. In fact, in stock form your car has PLENTY of fuel as it is. My advice would be to learn about tuning.

 

To increase power you need to increase airflow, not fuel flow. Fuel can only be burnt of there's oxygen available, not just adding fuel will not allow more of it to be burnt. In fact just adding fuel (i.e. a richer mixture) lowers combustion temps and results in less power.

Stick to the basics for now. Learn how to increase the engine's airflow (i.e. intake and exhaust) first.