Hi Gareth,
I was one of the first Turbosmart reps you spoke to about this. You probably didn't know, but that last guy you spoke to, was Nic, the owner of Turbosmart . I think he was kind enough to give you a free valve guide considering.
This issue was discussed among the tech staff and collectively, we have never come across an issue like this where it was the gate (Leaking or otherwise). The leak in your gate was marginal and technically would improve your power curve.
Can I reiterate what was discussed the other day, which is your AFR is way too rich. We suggest you find another tuner for a second opinion on the AFR values.
What stands as the first glaring issue, was the sheer density of soot in the outlet of the gate. It is running extremely rich on boost and if that gate came off after a power run, it is running too rich across the boost range. The amount of soot would indicate something in the 9.5-10.5 range. Consequently, comparing to your first power run, your plugs will foul up giving you a much weaker ramp up on the next run. This would get even worse if there were no air temp compensation values, allowing it to run richer as the air got hotter and thinned. This is something that would give you those graphs also. Your first, slightly cold, run would have been pretty good but as the car got hot, it got richer and would retard your spool up.
In contrast, you will find quite a few tuners will lean out the lower rev range in certain areas, to improve spool up.
The above is merely opinion and we strongly advise you consult a qualified and well experienced tuner before making any changes.
Hope this helps.
Cheers,
Troy