same thing happened to me. If you have a tuner, you know what rpm your idle is at, so run the car at normal idle and press on the gauge. My speedo is still off like 6 mph, but all the other gauges you can press on with they key in the "on" position b/c you know how they should be. The car is cold, battery should be in middle, & same with oil pressure. for fuel just run it till the low fuel light is on and then press that gauge on.
still seems kinda hard to drive and press on a gauge while looking at the test thing.. idk