Steve, whether or not they dialed the cam gear in perfectly from factory or not is irrelevant for all of us isn't it?
Everyone who has replied to this thread has upgraded turbos, and in most cases, MAJOR upgrades... Different turbos need different timing values to extract the best performance, and even if you had the stock turbo, you can play with bringing the turbo on boost faster, or choosing to sacrifice low end response for top end power...
I put an HKS exhaust cam gear on my GTS whilst having the PowerFC re-tuned, so I can't give you a pure power increase figure for the cam gear alone, but I *can* tell you this:
Before Cam Gear: 1.2 bar @ 4200rpm
After Cam Gear: 1.2 bar @ 3900rpm
For that alone, I think it was worth every cent, plus more