According to the VMX article issue 21 - 37.6 hp at 7000rpm which is less than what the PE250Z brochure says (38.5hp at 8000rpm & 36.0 Nm torque at 6500 rpm)
1.5 HP down on RM4000 between 3000-4500 rpm. Beyond that the PE400 ruled the roost, gaining an extra 3.5hp more than RM400 after 7500rpm
1981 400X brochure says 31.0 KW (41.5hp) at 7000rpm. Max torque 43.0 Nm (4.41 kg.m, 31.9 lbs.ft)at 6000rpm
1982 400z has same power ratings and torque ratings.
In the end i think the brochures probably exagerate a bit. if you want a definitive answer get yours dyno tested, otherwise just ride it and enjoy it.
All this info comes from my info which is also availble on Lukes Skydrive for all to see so you must not have looked there.
