I'd just like to give a shout for Regal Autosport in Southampton.
I've had a few problems with my 2005 GTI which were a bit beyond me, although posts on this forum were pointing me in the right direction.
It had just passed the MOT at a place I know are quite strict, but nothing had shown up which might cause a loud clonk when pulling away spiritedly, accompanied by lots more clonking and juddering.
Regal checked all the bushes and mountings, which were all fine, but put in a stiffer torque arm insert which has cured this completely without causing any vibration or harshness.
Also, my boost seemed to be lacking, despite a new rev D dump valve, shown both on my Polar Fis and the seat of my pants, which I felt might be the PCV. Steve's vast knowledge and experience with Golfs and the use of diagnostics equipment proved this to be the case, and sure enough this was cured with the installation of a BSH PCV delete kit. Instant boost return, which was confirmed by a dyno run showing 225.5bhp at 5933rpm and 276.8lbft at 3483 rpm (car already has a Shark remap.) I have a slight mis-fire which will be sorted at a later date as I ran out of time. I suspect plugs or coilpacks although both have been replaced recently. My Polar Fis shows a misfire on No 1 cylinder which you can sometimes feel on the road.
I was very impressed with the way Steve explained everything to me when I dropped the car off, and called me say what he had found and to give me prices before he went ahead with any work. Also, he didn't try to sell me anything I didn't need, but did explain that there were more things that could be done to improve the car.
Regal's facilities are excellent, their staff clearly knowledgeable, and their dog very friendly. If you're in the Southampton area I can thoroughly recommend them.
TonyZ