It would be unburnt fuel
Exhaust of an engine is a gas.
Exhaust leaks close to the engine.
An exhaust valve(s) staying open upon compression.
It could be timing is off. Need more info. Is it Fuel injected or Carburated? Exhaust smoke? Is it black? Black indicates alot of carbon built up. May mean the fuel is burning way to rich.
Could be EGR Valve.
No, an exhaust leak would have nothing to do with your engine timing.
No, not related.
For steam to come out the exhaust you probably have a bad head gasket or a cracked head. If the turbo had an oil seal fail it would cause blue smoke to come out the exhaust.
An exhaust restiction, like a clogged catalytic convertor
There are several reasons that can cause smoke two, out of the exhaust on your 1993 Chevrolet suburban. The most common reason is a dirty fuel injector.