While chasing an intermittent misfire I figured I'd do a quick write-up on how to clean and test injectors, I already have the injectors out so this is just on the testing part not removal

I use a small small syringe and a piece (about 1-2 inches) of 3/8 fuel line to create pressure, and I typically use seafoam for the flush and to check spray patterns, and a 9v battery with jumper leads to trigger the injector. Whatever liquid you use, it's best that it isn't flammable because bumping the lead against the battery sometimes creates sparks Fill the syringe and slide the fuel line over the syringe and the smaller end of the injector, I try to get it about a half inch up each way

Picture of the syringe, injector, and lead
https://photos.app.goo.gl/8D52T9uBzFHgQUyj6

clip both jumper leads to the contacts on the injector, and only one contact on the battery. You want to hook up only one lead to the battery so that you can tap the other lead and make it click open for just a second, you don't want it open for too long or you could overheat the coil
With gentle pressure on the syringe, tap the lead to the battery a few times and watch the spray pattern, I like to use a plate with water in it so that I can see the spray pattern easier, for my 96 4Runner a clean injector sprays 4 fine streams, in two pairs

If you have a clogged injector sometimes you can clean it by back flushing it, you do this the same way just with the syringe and hose on the opposite end of the injector

I was concerned about heat soak issues, so I preheated the oven to 190° and put them on a tray in the top shelf for about 20 minutes, then tested again. Don't put them in the oven until it is up to temperature, otherwise the coil in your oven could burn or melt the injector

Unfortunately this wasn't my problem, all of my injectors performed perfectly, but hopefully this helps someone else!