1999 Park Avenue Ultra Difficult and Gritty Steering

I had my rack and pinion replaced because my steering was getting loose, and afterwards, for about a week, it would be very difficult and gritty to steer on occasion (usually during/after highway driving). I believe it was also difficult to steer when first starting on practically every trip until it all seemed to be worked out. I talked to the shop about this, and they said it was probably some air in the power steering fluid in the rack, and apologized as they thought they had worked it all out when driving it. Well, by the time a week had passed, it wasn't doing it anymore. A few months later, it did it again while I was trying to turn left across two lanes of oncoming traffic to turn around in a parking lot (very hard to steer and gritty). It also did it the whole time I was turning around in the parking lot. That was a couple months ago, and it hasn't done it again since then. I checked the power steering fluid after that, and it wasn't low at all. I stopped by the shop shortly after that happened and they said they really didn't know what that could be, but it might be the steering pump. I have driven a 93 Park Avenue I had with no engine power, and it wasn't that hard to steer; about a week later, a tensioner pulley broke, and caused both belts to come off (and break the other tensioner pulley). While promptly pulling off of the highway (left across two lanes of traffic), it was also nowhere near as difficult to steer as when I had the problem that seemed to start right about the time I had the rack and pinion replaced.

I feel that it isn't likely to be the power steering pump going out since not having a power steering pump doesn't make it that hard to steer or have that gritty feeling, but I wanted to get some input and see what anyone else who should know might think. I believe the rack has a one year warranty, but I don't particularly want to go without my car to get it replaced again if it isn't the problem, and if it doesn't reoccur again, I'm not even sure I could convince the shop to replace it under warranty anyway. However, I also don't particularly want this to happen when I'm on the inside of a corner or turning left across traffic and bind up so tight I can't turn it at all. Any thoughts?

Do you have magnasteer? Click Here (http://delphi.com/manufacturers/auto/other/steering/gears/magna/)

I thought I had magnasteer (I am assuming magna-steer is speed sensitive steering), as I thought I had read something that indicated that the Ultra included that (or it may be that I thought it was included in the gran touring suspension and thought that was included on Ultras, but it may not even have that) in 1999 (among other dates). That said, I'm not sure if it even has that, is there an easy way to check? I do know it has always seemed way easier to turn right after an alignment, but then seems to tighten back up over time.

The variable effort steering system aka Magnasteer was standard equipment on the 1999 PA Ultra as a result of the GT suspension/handling package. Also, the GM RPO code is NV8.

So, HotZ28, do you think the magnasteer might be what is causing the symptoms from my original post (even though it started immediately upon replacement of the rack and pinion)? Is there an easy way to test the magnasteer?