My just acquired '89 740 w/ only 100k has hard steering at low speed when parking (especially if the wheel is turned quickly).

Steering effort is acceptable at higher speeds, though if one rapidly turns the wheel, it feels like there isn't enough fluid flow momentarily, or that the boost pressure drops for an instant, increasing the steering effort.

I noticed that the PS fluid was black as coal, so flushed the system until the fluid was nice and clean w/ no results, so installed a new PS pump thinking that was the problem.

Not so. No change in steering effort w/ the new pump.

Short of changing the entire steering rack, is there anything that would create or alleviate this condition (restricted line, something that can be cleaned in the rack)? My 240 and 965* were almost TOO boosted, but this 740 is definitely under-boosted!

Yes, the belt is tight, and not slipping, BTW.

Thanks,
Bob
*I DEARLY loved my 965, but it is awfully nice to be back with a nice low-tech red engine that I have ultimate confidence in for the really long haul!