The car pulls timing when stock, but only about 1 degree instead of 3. It is not a problem and happens to every tuned GTI. The only concern is when it gets around 8 degrees.

I don't care how many cars you've tuned, you don't know what you are talking about in this situation. Maybe you need to read about the FSI engine (bet you havn't tuned one of those) or the Bosch ECU in the GTI. But I guess the hundreds of pages and documents scattered around the internet and the big tuners like APR and Revo Technik are all wrong, and you know exactly how a car that you've never worked with is supposed to run.

And maybe if you truly did know all you say about tuning, you would know that running boost causes detonation, so while the timing may be OK at 2400RPM, at 4000 RPM under 21lbs of boost, det is going to happen, so you retard the timing to account for the early explosion.