Fuel

My 1991 Chevy S 10 throttlebody leaks gas after I shut it down I replace the injector what else might it be

Fuel regulator

The fuel regulator is in the TBI and the main component is the spring that creates the fuel pressure, so I don't think it is the fuel regulator. They usually get weak and not create enough fuel pressure. The injectors are leaking either because there not installed correctly, the "O" ring seal is crucial to make a seal, Or the injectors are just bad. They should hold back the fuel. And if they do get too much fuel pressure, the injectors just shut down and fuel still does not get by them.

You might want to get a rebuild kit for the top of the TBI if your using the old gaskets.

Follow the gas lines into back of throttle body and the bowl just above and forward of lines is the housing for the regulator. You remove throttle body to replace so you can see what your doing and also may as-well clean it and get the rebuild kit it comes with new regulator too, and go ahead and rebuild it. You could be getting a stream of fuel instead of a mist/spray also flooding you out. The rebuild kit has the tiny filters and O' Rings ect for the injectors, look on youtube/net/repair book for this procedure. It can be done at home, Some may say its too involved for a newbie but its way easier than a carb rebuild. Plus the kit has all the gaskets too. If you decide to do it yourself, have a clean area where you can take it apart and put down each part in the formation/pattern as it came off so you can see where the new items will go back together and when taking the lines off the back side use the correct wrench size, be careful when reinstalling them to not cross thread them or over tighten and also there is seals that you replace for the lines too as the old ones will leak if they are from 1991 (likely). Use throttle body cleaner (spray can, need 2 cans). Watch how the injectors come out and install in same position as removed and same side and not turned around backwards.

I buy some fuel injection cleaner sold to go in the gas tank and pour in a jar and pull the small parts off the injectors and put the injectors in the jar and go about my normal day, may even let them soak a few days if they are suspect and there are some test you can perform too and at connector to see if there is issues. If it sprays at all the soak most times remedies it. If it does not you can hook power to it and push cleaner threw it, which will clean it out unless injector circuit is bad(will not pulse), just buy another. You can go to junk yard and cut off the connector to injector and connect it to a small 12v lawn/motorcycle battery to test with.

Buy a rebuilt unit and install it, turn your old one in as core. rockauto.com has good deal on them.

After you have the injector powered up, attach a short piece (bout 8 inch) hose fuel line about same size as the top of injector but small enough to have to force it on but yet does not fall off and use a large turkey baster syringe with the plastic tube that narrows and screws on, take it off and screw in on the rubber hose, slide the hose on injector after you suck up a full tube of injector cleaner then push syringe plunger in, hold it over a container if doing this inside to catch the fluid.