There's no definate answer as there's many reasons for a car to smoke.
I take it you are refering to black sooty smoke rather than blue oily smoke, if so you need to start looking at a possible air/fuel imbalance, though a puff of soot when initially accelerated is normal, when you accelerate it adds more fuel but it takes a moment (and needs the added fuel to speed the engine) for the turbo to spool up and get the air in, hence the puff.
If you're suffering heavy sooty smoke more often it's more than likely there's a fuel/air imbalance.
This could be down to a range of things.
The air is measured as it enters the intake by the MAF sensor and the ECU will fire the fuel in to match (match what it's programmed)
Blocked air intake or filter will starve the engine of air.
A fault with the MAF may give a wrong signal and too much fuel is added.
Air leaking off after the MAF, so it's leaking after it's been measured and not reaching the engine will give the appearance of over fuelling (which is in fact right fuelling, just short of air it was expecting) and soot.
Faulty EGR operation (just because it's new doesn't rule it out) can reduce the oxygen in the air that's induced, less air will give the same result as above.
Faulty or worn injectors can overfuel, too much fuel is fired in, there's not the air there to burn it completely, so it runs rich and sooty.
Faulty signal from the ECU, the ECU may just be firing in too much.
(I've a hunch the ECU is programed to allow for a little wear of injectors, say after firing X million times the ECU's programming will alter fuelling to accommodate this predicted wear, but the programming isn't quite right!)
A fault with when the fuel is fired in, to early or late and it won't get burnt properly. Cam and crank sensor issues.
Fuel pressure fault, high pressure fuel pump not producing the required pressure can alter the fuel/air mix.
Diesel Engine Smoke Explained - United Diesel, Shropshire
