It would run Ok on the flats with a bad lift pump.
I'd start with John's recommendations of checking air, fuel filters, but also check for boost leaks.
A torn hose or loose hose clamp will cause what you are describing (losing power and black smoke under throttle)
Also, smoking on start up and an odd puff here are there are not really unusual, unless it is laying down a full smokescreen on start up.
Could you describe the color of the smoke? Is it always blue? White? Black?
Could also be a headgasket. Are you noticing any coolant consumption?