I have a TBI tester kit that I bought from JC Whitney. It connects at the frame where the fuel lines come through and connect to the fuel lines going up to the TBI. It works well just have read the pressure from under the car. I have since added a T fitting and an in-line fuel gauge at the TBI. Along with a adjustable pressure regulator and fuel injector spacer. All works well. So now I can read the pressure at any time I choose. I purchased from a company that had a link on one the pages on this forum. They specialize in TBI performance modifications.

 

I like the idea of testing mine at the TBI or under the frame, especially since some times my back just don't let me crawl under things anymore. I strapped the thing onto the TBI unit today and it shows the exact pressure that it does under the frame, so on days when my back hurts, I don't have to lay on the cold ground