I have a 1990 Chevy 1500 silverado 5.7 liter. When starting the idle surges for a bit. After a while will idle a little better. When driving has lack of power especially when going from stop. And does not sound right. When turned off the idle thing starts all over again. Help!

. Clean the Idle Air Control Valve, throttle plate, and throttle body with a spray can of brake cleaner--be sure to wear safety goggles. Afterwards, replace the air filter.

. Install a new Ignition Control Module (ICM).

A sticking or sluggish Idle Air Control (IAC) valve could cause at least some of what you're experiencing.
Use a good carb/throttle plate cleaner. Follow the instructions.
When you say "lacks power", is that like a hesitation? You may have a worn spot on the Throttle Position Sensor (TPS). If that's the case with your truck, replacement is the only option.