Some comments on performance. From your 'handle' (semirigid rotor), I'll assume you're talking about helicopter perf.
There are two parts to this for turbine engine machines in the civil world- the first part is the engine power available, which is in the flight manual to make sure the engine is putting out at least minimum specified power.
The second part is less than clear, as it doesn't tell you (in most light helicopters) about power required to hover. In most civil manuals, it comes out as hover capability.
Yes this would be done with things like clean blades, and absolutely properly set torquemeters and the like.
In service, there should be some way to make sure that you do meet the performance thats in the flight manual - the UK CAA is pretty good about doing this. Other authorities are different.
If you're not getting the performance that the flight manual says you should be getting, and you're absolutely sure you've got everything covered from a maintenance point of view, then I'd think about contacting your airworthiness authority. Maybe submit a Service difficulty report (SDR), or write to them with the specifics. Enough reports ought to alert someone in the authority to check it out.
The certifying authority signs up to making sure the hover performance is correct, so if it's not, they should know about it.