Down on power and smoking sometimes - 2006 Chevrolet Silverado 3500

By driving it like this there is a chance you could have done some serious damage to the piston heads. White smoke is usually a blown head gasket. The amount of smoke can sometimes tell you how serious the problem is. To be honest this could be the head, its gasket, faulty valves or seats, camshaft issues or even bent or broken push rods. You might have to do a full tear down on this one!

Probably down to the age of vehicle.

If it's white smoke, it's oil. If it's black smoke, it's fuel. Make sure you haven't over-filled you oil levels.
If it's worse when you first start it, the oil is leaking down from the valves. You may even have some debris preventing it from flowing back into the block.

Would you have more info on that? White smoke is typically a sign of coolant burning unless its just the typical smoke from a car warming up. You could have a very small head gasket leak that allows a bit of coolant into the cylinders when the engine cools down,(gap gets bigger) and when it warms up it seals up again. Also related to a hard start if coolant is fouling the spark plugs. The clanky sound, is it permanent or does it come and go?

Loosing coolant, white smoke= blown head gasket.

Oil and carbon tend to build up, creating restrictions in the intake manifold. Symptoms will be loss of power (sometimes severe) and poor fuel economy.

What color is the smoke? White smoke is moisture/steam - which can indicate coolant is leaking into the engine (head gasket going bad).
Have you noticed your coolant level going down? Check the level in the overflow tank and the radiator each day (after the car has sat for several hours) and see if it slowly goes down.

pump may need recalibrating or a kit through it
or you may have a cracked turbo

hey
there are couple of smoke type.blue smoke is oil, black smoke is fuel, and white smoke is water, if it clears after starting and running a few minutes it's probably your valve guide seals leaking oil down on top of your pistons, causing it to smoke until burned off and foul your plugs.

black smoke from exhaust means a rich oil/fuel ratio, sometimes it causes by a clogged air filter or a problem on fuel injection system.