The only problem the 2.2 might suffer from is that it was a very early adopter of the particle filter system - long before most people had heard of them. (Most dealers weren't that knowledgeable at launch time either).
This caused confusion - wrong oil will poison the DPF, as will outrageously low rev driving (changing up at 1500rpm all the time, for example). DPFs need to get hot to work properly.
I can honestly say that I had no issues with reliability in over 5 years and over 100,000 miles of use. I am wary of many so called diesel specialists - lot's of 'em are still stuck in the good old rotary or in-line pump days. The HDi engines are too complex for your average olde worlde diesel mechanic in my opinion.
The MAF might be the cause of your problems, the only way to tell is to swap it out and see. Let the car dealer take responsibility for this - don't interfere as it might compromise your chance to snatch a refund if that's what you want to do.
I'd still seize the opportunity to walk away if you are disheartened with the car, but that is a decision only you can make.
The boost control and turbine vane geometry are ultimately operated by vacuum actuators (although they are managed via the ECU, along with everything else including all the interior electrics).
The HDi engines are a positive improvement over the still excellent XUD-T series.
PSA was one of the earliest to deploy fully managed high pressure direct injection engines in passenger cars.
