As regards to your comment about performance, diesels offer equally as good acceleration as thier petrol powered equivalents, in some cases they are quicker. You have to adjust your driving style when switching between the two, as you say, diesel is all about low down torque and shifting early. Revving the engine has no benefit. If you look at the basic BMW 3 series 2.0l both the petrol and diesel have 143 hp, diesel does 0-60 a fraction quicker, and the top speed is a fraction higher too, but it has almost double the torque figure. The diesel also offers 40% better fuel efficiency. Then the road tax for the petrol for one year is the same as the diesel is for 5 years.
Well, they're torquey as long as the turbo is spooled...half of what I do in mountains is strategizing how to get the turbo spooled in time for that next 5% grade without getting too much over-speed penalty from my benevolent overlord employers.
Yes, keeping the turbo spooled up helps a lot. I had to fight with the turbo on my old Renault powered LeSharo, when in mountains. More that once upshifts on steep slopes were impossible, because the speed would drop off during the upshift to the point that the turbo would not stay spooled in the next gear. Naturally enough I have been accused of never learning how to drive it. Matter of fact, I had the same problem with a semi on a steep upslope. The truck would easily start from rest, but the time required for the engine to slow enough for the next gear also saw the truck slow to where the next gear could not be used. It is slow going in a semi in its lowest gear.
I have had the same trouble with one of the school buses I drive. It has an International T444E engine, and a four-speed Allison automatic transmission. It normally upshifts at about 15 mph for the 1-2; 30 mph for 2-3, and 45 for 3-4. One of the towns through which I sometimes drive sits at the bottom of a valley, and has a 20 mph speed limit. The bus shifts into second at 15 mph, and the accelerator has to be eased off to stay legal. The speed limit increases to 30 about the same place the upslope out of the valley starts. At 20 in 2nd, the turbo is not spooled, and the bus is a real dog until it slowly accelerates to about 25 where the turbo comes up. I suppose I could slow to about 11 mph so the transmission would downshift, then the turbo would stay spooled on the 1-2 shift.
Hard to know what to make of that, most cars will react differently to a dyno , some you have to unplug traction control, abs or esp sensors and the like as the car assumes as the front wheels are spinning and the rear aren't, you're in some kind of skid situation. My friend tried to dyno his Fiat punto a few years back and the ecu wouldn't let him accelerate at all, TC kept kicking in, so don't think VW are an exceptional to these results.
So my two bosses car's and my parents new Skoda all have the VW 2.0 TDI, so I'll keep you guys updated about the situation. It's probably more of an inconvenience than anything having to take the cars back, it shouldn't cost anything, and the road tax is based on C02 not N0x anyway, so there not likely to be any increase there. Some have suggested the fuel consumption may increase after the software update, not a problem for my mum and dad as they only do a few thousand miles a year anyway, but might annoy my boss who does about 20,000 a year. He gets close to 60 MPG UK in his 2011 Passat which is good for a big car.