This has been somewhat posted before but I found it lacking.
Go buy 4 o-ring kits, 1 for each injector.
Unhook your negative battery cable. Electricity and gas don’t mix.
Depressurize your fuel system by removing the gas cap. Despite this gas will drip, so make sure your engine block is COOL and NOT hot.
Remove the vacuum lines that are in your way of the 3 nuts holding in the fuel rail.
Remove the 3 10mm nuts that hold in the fuel rail.
Remove the bracket just to the right of the fuel rail that is holding it from moving. It is also 10mm I believe.
Slowly pull the fuel rail away from each injector, one at a time. Do not pull it far from the injectors, just get them out.
Use an air gun or can of air to get all loose debris out of the surrounding area.
Remove each injector, one by one, being careful not to get any dislodged dirt into the opening that is left behind. As soon as you can, I recommend plugging the holes with a paper towel or something. There will be crud all around the seals, so be careful not to shove any dirt into the holes when you do this.
Once all of the injectors are removed, remove the seals that have been left behind.
Each hole needs to be thoroughly cleaned. I used q-tips soaked in fuel additive. This was a tedious process, but I wanted to be very careful not to drop any of the junk I was cleaning out into the holes.
Disconnect the injectors from their electrical 2P connections. This takes a little skill, and maybe there’s a trick to it but i just took a small flat-head screwdriver and pried each side of the clip that holds them on up and away from its origin, until the connector would pull away.
Now, plug those holes, make sure you are not dripping gas everywhere, and take your injectors inside.
You will need some kind of ultrasonic cleaner, some cleaning fluid of some kind, purified or distilled water, and an AC adapter. I used a 5 volt AC adapter. Adapters from old electric razors work great, but any adapter that has AC output should work. You don’t need anywhere near 12 volts, but 12 volts might be safe.
I took the adapter and cut the end off, and stripped the ends of the wires bare. I then used two plastic shielded butt connectors, the kind you use to mate two raw wires together. These fit together perfectly into the connection on the injector. I stuck the wires from the adapter into these, and pushed the connectors into the injector. This should be a tight fit and you want to make sure the wires do not come loose. You can crimp them in if you like.
Fill the ultrasonic with the water and cleaner. You will want to rig some kind of method to put the injectors in the cleaner basket but not soak the connector. I just stood one end of my basket up until the fluid would only cover the right parts. You want both ends covered, but not the wiring obviously.
Once you have this figured out, and it is soaking, plug in the adapter and let it go to work. The adapter will run the injector at 60hz, or 60 times per second duty cycle. If your injectors are like mine at first it sounded exactly like my car did, sputtering, but then it cleared up right away.
I left the injectors in the ultrasonic for 15 minutes a piece.
Now, when you remove them, wipe them down but do not get anything inside the ends or near the pintle.
I recommend soaking the o-rings and seals in gas for about an hour to get them nice and pliable. If they are not pliable, you may put a tear or nick in one, then your work is for nothing.
Also, before putting the seals on, lightly coat them in vasoline. This will make installation easier, and will stop them from tearing. Put the wide seal on first, then the o-ring, then the large seal on the other end.
Reinstallation is the reverse of removal.
Don’t forget to reconnect your vacuum lines, etc.
Enjoy! I went from stuttering on throttle from idle to hard to avoid tire squeal.
just a quick ?. what the hell is an ultrasonic cleaner? and what solution did you use? pictures of what to use and how would really help. my car stumbles and gets terrible mpg. i may really need to do this
+1 for pics! 
Never, never, did I say never use H2O or H2O based cleaner to attempt to clean your injectors!!
Go to Chevron and purchase some Techroline or an auto parts store and pick up some injector cleaner.
Use DC current from a regulated lab power supply, AC current will over heat the coils and destroy your injectors.
Vaseline is for babies bottoms and sex, not for lubricating O-rings, use a Silicone lubricant or non detergent motor oil.
If your going to add to a previous post you better be dam sure you know what you are writing about and your info is correct!
ok. well, that doesnt answer my question. then maybe you can explain this better. do i need this ultrasonic cleaner or can i just hold the injector in the cleaner? what about just taking them out and sraying the cleaner in the hole while its hooked up?
If you haven’t a clue or little experence working with percision devices forget you even read this, take your injectors to a cleaning service pay them and be done with the task.
Yes, you need an ultrasonic cleaner, which uses brisk small sound waves through a medium to clean items. The general public can often find them at drug stores sold to clean dental appliances, silverware or jewelry. Most scientific labs use them to clean various instruments and a university biology lab is a perfect place to borrow one to use.
Only the tips of your injectors which house the pintle need to be submerged in the ultrasonic cleaning media, no where near the electrical connections. Something about the height of an empty overturned tuna can with holes punched in it should provid the correct depth.
And again never use a H2O based solution or media to clean your injectors, simply you will corrode the inner workings and end up with junk for injectors.
Injector Cleaning Service
I’ve used this guy when I did the EFI conversion for my Scout. He was relatively quick and very knowledgeable. He does ultrasonic injector cleaning for $16 each. Good for those old GM throttle body injectors that have been sitting in the junk yard for 10 years.