Taurus Warped Rotors?

Car is 1994 Taurus GL wagon, 3.8L, 4 wheel disc ABS brakes with 212 000 Km. After a few minutes of driving the rear wheels making "whoop - whoop" noise.
Only happens when driving slow (like in parking lots or starting again from a red light) and not pressing the brakes. Usually happens in the slow turns.
I thought maybe my a rotor was wrapped. Sent it to the shop because eventually the noise got really loud and annoying. Got new rear rotors. After a couple days problem came back. Back to the shop, changed a rear calliper (the other side was changed a year ago). Same result. Back to the shop, they changed one rear rotor (free)... the mechanic found rear bearings on one side could use changing soon but didn't think it was related. A few days the "whooping" noise is back.
Not sure if this is related but... For the last 3 years, I've been having troubles with vibrations from steering wheel and dash when driving @ 110+ km/h. It seems to go away @ 130 km/h. I always rotate my tires every season (front to back). I got my front rims balanced twice (16" Eagle Alloys mags with 205/55R16) but it still vibrates. I tried my winter tires ( 215/60R15 Blizzaks) on the front but the shakes were worse. Most likely the it's cheapo Firehawk FTX tires I bought from Sears 4 seasons ago. I took it to 3 shops to check the front end and suspension and they couldn't find any problems.
Any ideas?
email snipped-for-privacy@telus.netX (delete the X)
Thanks in advance
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