"Whoooing" sound 40-50mph

95 Escort 1.9 Auto trans. A couple months ago I satrted hearing this noise. most noticeable at 40-50mph if I just slightly let up on gas or accelerate slightly. Kind of sounds like the noise wind makes. I can't find any obvious vacuum leaks. Also, sometimes I can feel the car kind of stumble almost like it is going to stall, most noticeable when coasting. I had a stall at idle problem, would running very rough & stall after about 30 sec at idle... which was improved by replacing IAC. But I'm wondering if there is some sort of vacuum leak or trans problem that is root or maybe secondary problem. Any ideas? Thanks.

I dont know of any way the transmission or the torque converter would make a noise at all like a wind noise.
Make sure the large rubber air inlet duct is intact. The engine doesnt run as well if its split or cracked or not seated at its two ends. Next I would check whether the air filter is still in place and is on one piece.

Any older car is likely to make some strange noises at time goes by. I have known the plastic splash shield under the motor and in the wheel wells to start making sounds, as the little bolts that hold them in place come loose or dont get replaced by the mechanic. There were 4 parts to the original splash shields - all made of plastic. Few of our Escorts still have all of them.