I have an 83zxt and I have been slowly working on it for since I bought it in February. Since I got it the factory boost gauge hasn't worked. I was wondering what is the more common to break in these cars, the sending unit, or the gauge? I also have the digital dash and the gas gauge has never worked. Is that the gauge or the sending unit, or something else? This is my first z and any help would be appreciated. Thanks

Check out all of your vacuum lines going to the sending unit and then check all of your electrical connections. It likely isn't the gauge but you'll never know until you start checking and testing everything.