Posted by: @angus

What is the best cleaner to use when cleaning fuel injectors: Brake, Carb or Throttle body cleaner?

Fuel injector cleaner.

Posted by: @angus

Also to open the injector does polarity matter? I don't want to fry them.

Yes polarity matters, and so does pulse width. You will fry them if you try to mess with them yourself. Just put the cleaner in your fuel tank.

To help you properly we need complete information. Post your vehicle details ,symptoms, etc.

Fuel injectors are electromagnetically controlled (solenoid) valves. They don't care about polarity. On the electrical side they're just a coil of wire wrapped around a moveable plunger. 

When the coiled wire is energized, it becomes an electromagnet because a magnetic field is generated around the coil of wire and the moveable plunger inside the injector is pulled up towards the center of the coiled wire. It doesn't matter which direction the electrons are travelling through the coil of wire, a magnetic field will be generated. You can use one of those square 9 volt batteries like the kind found in most home smoke detectors to energize the coil

But maybe consider saving yourself all that time and work of pulling out the fuel injectors and use a fuel injector cleaning kit. Scotty did a video on these things a long time ago. You need to have an air compressor to use one. But a really cheap air compressor is all you need. These days you can buy these types of things online for around $50.

https://youtu.be/bKGI9N_yWd0?t=47

This YouTuber uses Alcohol. 

Start at 16:30

https://m.youtube.com/watch?v=tRM-n15tuXs

On numerous occasions Scotty has highly recommended ATS Carbon Clean.  They are not cheap but he has had good experiences using it in his customers’ vehicles.

See below:

https://www.atscarbonclean.com/product/case-of-505crf-fuel-system-treatment/