Stiff steering on '92 Lexus LS400

My first thought is if it is a remanufactured steering rack and pump, there could be a bushing, or other item, that was not replaced correctly. Remanufactured parts are never as good as the factory. It is near impossible to repair anything to the tolerances that the car manufacturer has the ability to.

You might try to get the rack warranted and/or the pump. It sounds more like the rack as the pump is going to usually make noise if it is not working right. Check for play on the power steering pump pulley and make sure that the power steering pressure switch is connected.

Your mechanic might have some more ideas now that he can step back from the car. I know I always need a break from working on my car to stop, "beating my head against the wall", before I can think of other possibilities.

I hope this helps. I will keep any eye on this post, so let me know how it goes.

Check P/S fluid in reservoir with engine running is it foamy?