'99 Grand Prix 3.8

I had a problem with a vibrating steering wheel when braking but that is now fixed (warped discs). Now there is no vibration when driving straight or braking.

Now a new problem. When I am driving on a straight road and turn the steering ever so slightly on the curves (40-50 mph), I feel a very slight resistance in the steering wheel. This is not a strong pull, or a noise of any kind. The resistance is not steady either, it feels like it pulsates, almost as if someone is grabbing the releasing the steering column very fast as I try to turn.

I am able to turn and drive without a problem, but this is a bit bothersome.

Have read that possible causes are low PS fluid, leak in the R&P or needing a whole new R&P. Any ideas or things to check?

If it the R&P, is this a DIY job? I have a good jack and stands, but no access to a lift. I have done front ends, tie rods, bearings, brakes, etc.

Thanks