Gentleman,
I am not a guru on the Arriel 2C or 2S series engines but I can offer some explainations based on my experience with the 2B series which is very close.
When the engine is calibrated on the test cell they actually bend slightly the nozzel guide vanes. After a short time (within 700 hours or so from new) the NGV seems to open up just a bit which reduces power and makes the engine run cooler. Turbomeca has figured this out and changed the test cell criteria such that an engine with 700hrs does not fail a power check. Now the engines right off the test bench make a good bit more power and therefor run a touch hotter. Normally this is not an issue but if you are running in a high temp environment you could be pushing the T4.5 limits right from the start. The folks in the shop are given a range to shoot for when calibrating an engine and they have to guess at the type of environment you will be operating in so they can produce an engine that fits your needs. Unfortuantely until recently they were not getting much feedback from the field as to where their best guess was hitting. They have to use Kilowatts and T3 temperature in the cell where as on the aircraft with installation losses and corrections the numbers may change. The test cell guy doesn't know that so many KW and so much T3 is going to equal a certain amount of Tq margin and T4.5 margin in the aircraft. They are getting this info now so they should be able to set the engine up a little better in the future.
The Arriel 2 series in general is still a fairly young engine and of course has had it's growing pains. As was mentioned previously it is getting near it's upper power limits which creates some challenges. Another issue that has become a problem is premature engine removal. Since the engines are FADEC controlled some of the old school type maintenance staff would rather change an engine than troubleshoot to see where the problem really lies. I don't want to accuse anyone of this as most of the maintenance folks I have met are top notch but it does happen. I have seen several engines removed for indication problems and lack of troubleshooting. This situation as well is getting better but the damage to the statistics is probably already done.
I would be happy to unofficially try to answer any specific questions if I can but as I said I am not the Arriel 2S or 2C authority.
Best Regards,
MaxTork