N1 fluctuation
As Blackhandler is writing it could be the bleed valves to check this you have the closing point check (Bubble check) in the P&WC EMM. My experience however is that BLV problems is affecting all the parameters and normally result in lack of power. However the check is quick and easy.
As for the flow divider once the engine is started and in idle the flow divider has done it's job. Normally problems with it would be hung start or very slow acc. during startup.
If you are sure that the N1 is the only fluctuating parameter and the ITT and FF is steady I would say it's an N1 indication problem. Try swapping N1 gauges and after that the N1 tacho gen.
Does the aircraft have an ADAS+ system installed? If it have you are welcome to send me the download from it for a quick analysis...fee of charge