I just had this same problem, but it turned out to be a smog pump about to lock up, i bypassed the the pump and it is cool, now my p/s pump is going bad
but i noticed by putting a long screwdriver to the parts and listening where it is (be careful while motor is running)
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90 lx coupe: 5spd, energy susp trans mounts, fms hd clutch, Mac coldair fenderwell, Mac h-pipe, supercoil, ADS chip, 160 stat, aluminum D/S, Black magic fan, 3.27grs.
Best time: 13.9116(on 225/60/15 firehawks)
Best mph: 98.17
Best 60': 1.9607
someday mods:4.10's, slicks.