this isnt necessarily a bad thing. even at idle there will bea small ammount of pressure on the rear in an auto. shifting back and forth from D to R you should feel the car shift as it clicks into gear

 

I do stop all the way and i had driven my car for about 7 months now so i do feel like its not normal to shift that hard. So i did replace both the O2 sensors and the car began to hesitate a lot again so i just took it to the shop. The shop connected the computer and it said that the MAP sensor was not responding and the shop told me that there is something electrically wrong with my car. Ill keep the pple informed during the next couple of days.

 

Bought my '94 auto a couple years ago having what sounds like similar complications. Auto shops were blaming the MAF sensor also. Finally found a mechanic that pointed out the distributer (origainal on 160,000k at that time), replaced it with a rebuilt and the engine has purred like a kitten ever since. 180,000k now. Could be a coincidence this happened at the same time the headers were installed, worth a check though.