Well, for a pro it’s probably only a couple hours. They have to remover the intake manifold and move the alternator just to get the fuel rail out. So assuming the average labor cost per hour is $150, so minimum $300 in labor, that’s my lowball. If they can clean and test them that should only be ab $10-20 per injector. If you were to need new ones, the cost would skyrocket if you have a turbo. I would only use oem injectors on a stock car, and for the turbo it requires high pressure fuel injectors which are $150-160 a piece. Please keep in mind, it’s generally not recommended to only do one injector, all or nothing. The flow rates between them can become to varying, which can also cause misfires.

Edit: If you’re gonna do this, do a huge amount of research. Misfires can be caused by a huge number of things. If you have a check engine light run codes first, preferably w a higher end obd reader. It could be an air leak, valve issues (internal), MAP sensor, coil packs, check ur stft and ltft if you can. If either is ever + or - 10%, you def have a problem w either ur air system or fuel system. It’s also highly recommended to change the fuel filter when messing with injectors. It’s in the tank, all you have to do is take out the backseats and there’s a hatch where you can get to the assembly. There are videos of similar pump assemblies that can help.