Just thought I'd follow up on this -
I attended the AMD GolfGTI.co.uk rolling road day on Saturday, with my standard pd 150. I was on about 7th or 8th after a late arrival (muchos beer the night before :-[).
I had been told be several people that the PD's often leave the factory producing more power than the name suggests, with some people getting 165 bhp straight out of the box!
Imagine my surprise then when my totally standard 60k mile example turned out 186bhp and 279 lb ft of torque!!!
Had it just been mine that had been on the rollers I would have suspected over-generous rollers, but based on what everyone else was seeing, it turns out that these are pretty much bang on.
On that basis I don't think that I'm going to bother with a tuning box. Most of them promise only 190bhp without further mods (zorst and filter) and I'm running damn close to that now - I'm certainly not spending ?400+ for 4bhp!!!!