Tranny fluid in p/s system

i have a 95 740i that i mistakeingly put wrong ATF in p/s system i have since replaced pump twice the second time around i blew system out and put in dextron III which it calls for if all the old fluid didnt come out am i looking at replaceing yet another pump?

Honestly, with most cars it probably does not matter much what trans fluid is used in the PS. What did you put in instead of Dex III? Where did you buy your replacement pumps?