Here's technical specs on the IUS stages:
SRM-1 empty mass: 1134 kg
SRM-1 nominal propellant load: 9631.8 kg
SRM-1 minimum propellant load: 4815 kg
SRM-1 average thrust: 184752.84 N
SRM-1 delivered ISP: 2898.855
SRM-2 empty mass: 1170 kg
SRM-2 nominal propellant load: 2727.45 kg
SRM-2 minimum propellant load: 1350 kg
SRM-2 average thrust: 78272.76 N
SRM-2 delivered ISP: 2977.335
The IUS Reaction Control System consists of twelve Reaction Engine Module(REM) thrusters and nominally two 55.125 kg N2H4 monopropellant tanks. A third tank can be added on customer request. A tank can also be deleted upon request.
The IUS RCS is enabled by the IUS computers when the separated distance between the orbiter and the IUS is at a minimum of 120 m. The thrust of each REM thruster is 157.6 N(as far as my memory goes!).