Land Rover Repair: Freelander 2.0 TCI diesel cold starting/driving, mass air flow sensor, throttle position sensor

Question
Sir,

I just overhaul my 1998 TCI Freelander 2.0 diesel.
Renewed all the pistons rings, Renewed  also piston no.3, all valves and valve seals. When starting the engine starts without hesitating, at once. Engine idles perfectly.
Back out the car from the garage with no problem. When i give gas to drive forward the engine seems like it wants to shut off. I keep the engine running by balancing the clutch and fuel pedal. Then the car rides forward slow and  still not responding directly to the gas pedal. After a while when giving  gas the engine Rev up with a big   release of grayish  smoke cloud.  It is as if something is holding it back. Hereafter the car is full of power. Accelerating perfectly idling with out problem, only with a small plume at the exhaust.
What can be the culprit of this: throttle position sensor, Mass Air flow sensor, Manifold atmospheric pressure sensor, clogged exhaust piping?

Awaiting your reply.

Hubert

Answer
Sorry for the delay, I had a long think on this one.  From your description, I gather the engine will not rev up when cold, even though you can maneuver the vehicle in reverse.  The puff of white smoke leads me to believe you have one or more faulty injectors and/or a stuck EGR valve.