First of all - ground it. If you superiors disagree give the CAA a call for backup. I'm sure they'll insist it be grounded.
Secondly, get on to the engine overhaul facility and get a copy of the work pack. Everything they did to that engine will be documented. Take it to an independent maintenance organisation and have them go through it and ensure everything is in order, correct parts used etc.
Limits are there for a reason - it usually is the case that it's fine to operate above those limits, but this is for a transient period only. To routinely operate above the limits is a definate no-no.