so i have a 99 2.2l 3spd auto. i will be driving on the highway maintaining 75 mph and suddenly it will feel like i'm hitting the brakes for a few seconds, then will go back to running like normal. then a minute or two later it will do it again. it does this continually on my 45 minute drive. if i keep it around 60 it won't do this, but 70 on up it starts. around 80 it doesn't seem as bad. the engine does not change revs sounds completely normal with no sounds that aren't normal. anyone have any ideas?