Differences between OBD-I & OBD-II

[Greg_Coombs@esd.tracor.com]

     I am sure this topic has been covered in depth before, but I would 
     like to get some different viewpoints on the subject.
     
     I am in the market for a '95-'97 Jetta GLX or Trek and I will want to 
     do some mods to whatever I buy.  In talking to friends, I have heard 
     that there are major performance potential differences between the 
     OBD-I ('93-'95) cars and the OBD-II ('96-up) cars.  Specifically, the 
     OBD-II cars don't respond to performance mods as well, don't have a 
     dual spring setup for the exhaust valves (which, I'm told, means an 
     aftermarket cam with any real amount of lift will make the lifters 
     float at high rpm), the throttle response is not as snappy as the 
     OBD-I cars and the throttle body cannot be changed to a larger unit 
     because the idle stabilizer unit is built into the throttle body.  I 
     want to know if these problems and changes are true and not just 
     hearsay or one person's bad experience.
     
     Any input on this subject would be appreciated.  I don't want to go 
     out and spend $15K on a car that I will be sorry I bought a year from 
     now.
     
     Thanks,
     Greg Coombs