15 minute test flight sounds a bit silly to me, especially if part of the cover was missing!!
Call tech rep first, if you can't find a procedure for suspected FOD injestion.
Start with the easy stuff. Remove the mesh grill from the intake and feel for damage on the first stage compressor. Insert borescope down compressor and check further stages, and impeller, if you can.
Remove an ignitor plug and borescope the combustion liner checking for damage. Insert the borescope guide into said igniter hole, and check the Nozzle Guide Vane, and Compressor Turbine.
Any damage found, refer PT6T manual for limits. No damage found, ITT was in limits, compressor didn't surge, then all should be OK.
Spanish Waltzer, if you don't trust your engineers, maybe you should change jobs. They undergo 10,000 hours of practical and theory training just to get a basic licence, then extra requirements for each type rating on top.
Call Agusta (there should be a P&W rep there), or call P&W direct. They should be able to help. And pleeeeeaaassssseeee tell them EVERYTHING. I have been involved in fault finding where the pilot didn't want to tell us everything because he thought he would look silly. After 5 days trying to trace and replicate the fault, we finally got the whole story, and went straight to the problem.
Apart from the 15 minute trest flight, I agree with tuk tuk boom boom.
Regards