I've been running mine on 134 with the original condenser (W126 and 7 cylinder) for maybe a month. The belt has been tightened about three or four times now. I get to around 58 degrees, no matter the outside temp. It feels colder than that, and the compressor cycles, so I think I'm going to check my thermometer. I think I have too much 134. I put right at 36oz in. Something to play with over the summer.
Anyway, I have a "harmonic" now that was never there before, with the AC on or off. Probably wouldn't notice it if I didn't know it wasn't there before. Doesn't have anything to do with steering, though. It really needs a 1/2" belt to match the crank pulley, and I wonder if my harmonic isn't caused by the 3/8" belt riding down in the crank pulley. I'm looking for a 1/2" pulley compressor clutch in my spare time.