The pix below shows the voltage regulator for an instrument cluster from an '86 (mine). Your '93 is probably very similar, but I know that it's not idential. However, the VR is probably the same.

The VR controls the voltage that drives the temperature gauge AND the gas gauge. If both gauges misbehave the same way (e.g., both read too high or too low or both are dead), then the VR is probably the cause. But if one gauge behaves properly while the other misbehaves, the problem is likely to be elsewhere.

Keep in mind that the gas and temp gauges are mounted to the circuit board by two studs (each). These studs also act as the electrical connections. If the mounting nuts loosen, then either or both gauge can become intermittent. In the picture below, you can see the four nuts near the VR.

Be sure your nuts are tight.