I don't think he's wrong. The SCV in the YD25 ran me about $280 but a set of injectors from Nissan is $4K, we found a set of genuine Denso injectors (to match my engine) for $1500 on eBay, still dearer than the SCV regardless. The MAFS could just be dirty and is easily cleaned but ONLY with electrical contact cleaner fluid (also sold at auto places as "MAFS Cleaner", same stuff). You take out the MAFs, spray this in the little hole and watch the black stuff pour out. When it runs clear you hold it for about 30 seconds before reinstalling to make sure all the cleaning fluid has evaporated.
You might also pop your intercooler off. It has two openings. Grab a can of petrol (who cares what kind, E10 is cheaper and just as good). Put your hand over one of the openings, with the intercooler resting on that hand, and pour about 100ml of petrol into the other opening. Put your hand on the other opening and turn the intercooler up the other way so the petrol runs down through the cores. You'll find it will build up pressure as you do this, release the UPPER hand (or you'll be sprayed with black shit that won't come out of the clothing, ask me how I know).
I do that 5 or 6 times until the petrol comes out showing some of the colour that it had when it went in and it does help.
Liqui Moly sell an injector cleaner that is pretty bloody good, too. It even helped prolong the life of my SCV there for a while, so give that a try - "Fuel System Treatment". You can also use the Diesel Purge, but that's a bit more fiddly (although it's also quite a lot faster than the one you throw in the tank).
Finally - if all else fails - you would have to start considering the turbocharger. It's cheaper than injectors too, and in my experience fails sooner than the injectors do. That would be time for analysis of the boost pressures being produced though, and an investigation into the boost control device. On my YD25, a vacuum produced by the engine is modulated by a Boost Control Solenoid (BCS) and this is then fed to the diaphragm of the actuator on the turbocharger. I've replaced my hoses twice, and the BCS twice, and now I don't use a BCS at all, I'm using a Tilix valve to control the boost. The Tilix valve works pretty well, to be honest, and is cheaper and more reliable than the BCS. There is no check engine light for a failed or faulty BCS in my car. Yours will very likely be different, as in 2011 or thereabouts they changed the turbocharger's vane control to electronic. Yours might be faulty - you won't know until someone with experience of that turbocharger takes a look.
