Your fluid is probably pretty dirty by now. You could try flushing the system out. It's a little time consuming and maybe a bit overkill, but it should get the job done.
Get 3 bottles of cheap power steering fluid and 1 bottle of a higher quality fluid; I use Valvoline SynPower.
Remove a hose from the P/S cooler or from the metal line near the oil filter (whichever is easier for you), and let the fluid drain out of the fluid reservoir. Put the hose back on, and refill the reservoir with the cheap fluid.
Start the engine and turn the wheel back and forth to the extreme left and right several times to circulate the fluid. Stop the engine, empty the fluid again, refill it with the cheap stuff, and repeat the process. Each time you empty the fluid it should start looking a bit less muddy. After you've finished off the cheap fluid, refill the system with the Synpower fluid.