What was found
FLT#253, FLL-SJU (AIRCRAFT PERFORMED AN AIR TURN BACK TO FLL). ' AUTOPILOT DISCONNECTED IN CLIMB ABOUT 20,000 FT. MULTIPLE EICAS MESSAGES APPEARED, AMBER STICK SHAKER ANTICIPATED #2, BELOW AT FAILURE. LATER ABOUT 15 MINUTES IRS FAIL APPEARED (#2) ALSO. RAN QRH'S & RETURNED TO DEPARTURE AIRPORT; ALL FAULTS CORRELATED TO "IRS DATA INVALID OR MISCOMPARED". AT ARRIVAL "IRS 2 FAIL" DISPLAYED ON EICAS WITH PFD2 FAULTED.PER FIM 34-26-00-810-808-A WITH FC#34265515IR2. REMOVED AND REPLACED IRU2 PER AMM34-26-01. OPS CHECKS ARE NORMAL. A/C OK FOR SERVICE.'