My 94 Silverado 7.4 idles fast

The idle is controlled by the Idle Air Control Valve, IACV. It is located on the intake manifold near the throttle body. It will have an electrical connector or a vacuum line running to it and sometimes there are coolant lines running through it.
The other possibility, this is not as likely, is the throttle position sensor, TPS. It may have failed and needs to be replaced.

I am giving you a link to a diagnostic walk through that will cover these issues as well as other possibilites. It covers each in depth as how to locate, test and repair the problems that cause high idle.

Here is the link;

https://www.2carpros.com/articles/engine-idles-too-high