I agree with getting boost numbers first, having that sort of information could help prove the turbocharger and its control sections are innocent.
Also, what colour smoke are we talking about? Whitish/greyish or black? I wouldn't expect blue smoke to cause a problem unless the turbocharger bearings had failed, oil was being pumped past the journal bearings into the exhaust - that's clearly not the case since you've noticed boost working.
If you're getting whitish smoke, you might have a DPF sensor fault. You don't say whether it's a manual or an auto - DPFs were only in the autos - so if it's a manual, forget this paragraph, but if it's an auto - you will need to do something about the DPF. There are a couple of options.
1) DPF Delete Pipe. Generally around the $1100-1200 mark. I can only assume it comes with new sensors, and is not the path I took.
2) Replace DPF with a 2nd-hand one. Definitely something to consider, most cars don't become wrecks because of a DPF failure, but consider giving it a clean before installation.
3) Replace DPF with a new one. Not from Nissan - they want $4K (or your firstborn) for one, but you can get aftermarket ones.
4) Hollow out the DPF yourself and fit a pair of DPF sensors ($600, when I bought mine) from auggie on this forum (send him a private message). This is what I did. My car does now blow black smoke on takeoff, and the inside of my exhaust is now black, but I have no DPF issues, no false limp modes and basically no worries. I changed the sensors over myself, takes about 15 minutes which includes getting my old joints under the vehicle and hunting around for the spanner my arthritic hand kept dropping.
Black smoke is a sign of too much fuel for the air the engine is getting. That could be turbo - either the turbo itself or its control mechanisms - but if you get an OBD2 reader/BT+app, and see that under acceleration you're getting around 18-22psi of boost, the turbo is delivering and the fault is elsewhere.
Consider cleaning the intercooler - remove from the front of the car (two bolts, plus two hose clamps, after removing the grille for access). Pour about 100ml of petrol into it with one hand covering the lower opening, then cover the upper opening and invert it, releasing pressure from the upper hand. Repeat 5-6 times or until the liquid coming out is starting to resemble the colour of what went in.
You might also consider cleaning the MAFS - it's in the back of the air tube just out of the air filter. Remove the screws and gently pull it out - don't stick ANYTHING in it, it will be destroyed ($400 from Nissan) - use electrical contact cleaner (Jaycar), MAFS cleaner (Supercheap) - don't use degreasers, solvents or petrol, it's an electronic circuit.
