What was your process for flushing it?
Under the hood on the driver's side next to the fire wall up high there is a rubber return line w/ a spring clip holding it on. It's real obvious and the only one there. I removed the clip and hose, then attached a piece of
clear 3/8" tubing 6.5ft long onto the fitting using a small hose clamp. Ran the other end to a catch pan on the floor. Start the truck, in park, slowly depress the brake pedal as far as you can and hold it. Then turn your steering wheel clockwise 1/4 turn, back to center, then 1/4 turn counter clockwise then back to center. Slowly release the brake and re-apply and turn steering wheel again. Continue this until you hear the pump make noise (mine took 3 iterations).
Stop immediately and turn off truck. Fill the power steering reservoir with fresh power steering fluid ( I used NAPA brand which is actually valvoline $12.99 a gallon). Then repeat this procedure until you see clear fluid coming from the hose. Make sure that you put something on the hose in the catch pan to hold the end of the hose in the pan. Mine took a little over 3/4 of a gallon. Probably more than I needed but I wanted to get as much old stuff out as I could, and like I said, the old fluid was BLACK! Then, remove the clear hose and reattach the rubber return line. Also, make sure there is enough new fluid left over to refill the power steering pump when you're done. AND, after you refill for the final time, start the truck and move the wheel back and forth, then recheck fluid level, add if needed. All done.
I can't take credit for this procedure somebody else did a really good write up on it with pics (HookMHornS I think?). Not sure if it is here or at the other place...

Look in the DIY or Maint. threads for power steering/Hydro-boost flush.