Downshift transmission problem 97 taurus??

Any opinions on this problem would be appreciated. I just got a My 97 Taurus automatic 3.0L Vulcan with 87K miles. It shifts smoothly on acceleration but on slowing down when I get to about 10mph there is a noticeable slight jerk. Is this a transmission problem? Or should I be looking at something else?

Also on releasing the gas pedal it seems that decelleration is very slow. eg. if I am going 50mph and release the gas pedal (not pressing the brakes) then it seems to cruise at 50mph for 2-3 seconds before slowly, slowly decellerating. Is this normal?

I also have the same problem, but with a high idle problem in park (goes up to 1500rpm), and when i shift into drive/reverse, the car noticeable jerks. It happened about a month ago, but went away after i switched over to BP gasoline and now it's back. Also, at stoplights the car also idles higher than it normally did. Any help? thanks!

dave