Thought I would add my experience here, with a good well looked after 300tdi CSW 110 on standard springs and original height.
starting point was it would do 70 at a push, 50mph up a hill, needed the lower first gear to get any speed quickly, but would pull away in 2nd. no smoke on acceleration. clean standard intercooler and good radiator. Egr blank already fitted on egr never there? silicon hoses old. did 5000 miles... and London to Santander took about 18 hours door to door.
I first added a boost ring and boost pin and immediately saw a difference in drive ability. and could set-off in and accelerate away in 2nd. a bit of black smoke on hard acceleration.
then added the alisport double depth intercooler and new silocone hoses and an egr temp gaugue. as far as I can see fuel pump still unmolested. did London To Santander in 14 hours. plumes of black
smoke on hard acceleration. will hold 80 on the clock (120km/h on GpS) loaded up a steep hill in 5th, EGT temps never over 600°C. another 5000 miles totally different. cruising at 70/80 is not scary if you adapt driving (I also drive through night to avoid traffic). lots of black smoke under hard acceleration!
fitted the billet turbo cartridge post not knowing what the heck was wrong woth boost failure and finally replacing wastegate as well which was full of black oil (turbo seals?)
need to shorten wastegate arm as at mo running much less boost and kicking in too late, but not taking the manifild off again
in a hurry! but will let you know and probably fit a boost controller so can get to just under 700°C when needed.
will also fit ashcroft 1.2 ratio at some point as the extra power makes it clearly under geared.
In my opinion the tuning was worth it in that it makes it easier to drive around town, and getting to where you want to go it now doable (slowing down to 50 on a hill was just a pain). The low down grunt of 300tdi is stull there if not better, you can leave it in silly high gears / low revs and it just keeps pulling. fuel economy on long trips at least increased dramatically. think if its the £100 boost pin and boost ring probably paid for itself in one long trip! if its the alisport intercooler a bit longer! Only downside is more smoke - however I have discovered this is a new passtime to play with tailgaiters / people who have full beam / fog lights glaring behind you... engage smog screen Q