1997 Buick Lesabre Buick lesabre surges

Im having a problem with what feels like surges in my lasabre. When i drive at highway speeds and the engine is warmed up it tends to feel like my engine is surging. It seems like a very common problem with these cars, but I cant find a definite answer to fix it. I took it in to a couple shops and they all said its hard to pinpoint it because the check engine light isn't on. (they all told me different possible solutions from spark plugs to oxygen sensor to fuel pump to engine coolant temperature sensor and so on.

here are some examples of the almost exact same problem Ive been having:

http://www.car-forums.com/talk/showthread.php?t=1951
http://www.automotiveforums.com/t665645-95_buick_lesabre_help.html
http://www.thirdgen.org/techboard/v6/61724-lazy-o2-sensor-1997-a.html
http://www.automotiveforums.com/t899276-1997_buick_lesabre_surging_and_tach_problem.html

please help :(