The issue is oil from the turbo, being recirculated back to the engine mixed with the hot recirculated gasses from the exhaust - which is a really bad idea, at best a botch to improve NoX emissions when a vehicle leaves the factory. The problem it causes is the oil is burnt by the hot exhaust gases, choking up the EGR, the intake and the valve ports. The parts are not on any service schedule for cleaning, so soon the engine is so choked up the emissions become much worse than they would have been without the EGR system at all. There are EGR bypasses, which can be bought for many diesels, including the BMW engined Freelander. The MOT cannot presently check for Nox emissions and a bypass fitted is not easily spotted.
I don't see it as inevitable though. Before this Freelander, Mrs Avocet had an X-Trail. I saw so many scary photos on the owners' forum of inlet manifolds that you could barely shove a pencil down, because they were so choked with crap that when hers hit 100,000 miles, I thought I'd best take it off to have a look. What I found, was... absolutely nothing! A light coating of oily soot round the walls of the manifold, but by "light" I mean something that could come off with a rag, rather than be scraped off. The car (in the 60,000 miles that we'd had it) had never done a run under 5 miles, and would get an "Italian tune-up" once a month or so. This Freelander (which was always very gently-driven) and now that I have cleaned it out, it is showing no signs of building up new accumulations, even at 155,000 miles, under the same regime.
I'm also not convinced that very much comes past the turbo seals (unless they're knackered, obviously)! I think the vast majority is crankcase fumes, but have no way of proving that.
I'm fundamentally against blanking-off EGRs (or disabling any other emissions control device), to be honest. It's not that I'm some raving tree-hugger (I wouldn't have a 2001 diesel 4x4 if I was!) but I do, at least feel somewhat self-conscious about it and try to keep the miles down, and keep all the emissions control devices as OE. As a 2001 diesel, the only MOT check is for smoke. There's no Co or HC check, so I could bin the cat, if I wanted. As you say, they can't even check for NOx. However, the practice is widespread. Pretty much every car mechanics forum you go on, there are threads about deleting EGRs (and other things). The trouble is, we're "peeing in our own swimming pool", for want of a better expression! Our air quality in cities and near big roads, is pants. The authorities are responding by bringing in low emissions zones and, more recently, reducing motorway speed limits on certain sections where air quality is bad. IF we (consumers in general) keep disabling these devices, we're only going to end up with more of the same measures...
