have just done the ATPL(H) instrument, and a/c systems, POF, R nav & coms. We learned, and there were questions on (for instruments):-
Pitot/Static stuff. Al your gyro stuff, including errors in various hemispheres etc. Engine RPM etc . EFIS, TCAS, IRS/INS, FMS. We all complained about some f/w stuff, i.e anything that mentioned Mach no's.