The surging sounds like the same problem the factory cruse control 
     engenders.  It's not a problem with the cruise control system.
     
     As it was explained to me, when the cruise control is operating, the 
     throttle valve positioning is so exact that the Injection System's 
     "brain" thinks the throttle valve is busted.  It goes into a "limp 
     home mode" which is not intended to be highway speed. Consequently, it 
     surges and bucks.
     
     Solution seems to be a $100 part which consists of an extension to the 
     throttle valve wiring.  Some sort of magic connection in the unit, 
     defeats the erroneous sensing and makes the car run ok on cruise.
     
     My local parts guy put the unit on my car right after I got back from 
     buying it in SC.  He said I could pay him once I had determined that 
     the problem was fixed.
     
     -Blaine
     
     P.S. This (along with a lot of other "standard" subjects) is one that 
     should be part of a FAQ somewhere.