2000 and up Vipers are called creampuffs because:
1- They switched from forged to hypereutetic pistons which can not handle boost or Nitrous as well
2- Although the cam has the same lift and duration, it has 6 degrees less overlap - not as lumpy.
Also, due to this cam change, pre-creampuffs respond much better to mods.
3- Creampuffs have ABS (2001+) and other creature comforts.
The funny thing is, my 2001 has a very lumpy cam, I'll have to listen to my buddy's 99 GTS to see if there is a difference.
Also, the lighter cast pistons supposedly make up for the less overlap cam stock vs stock performance.
Hope this helps,
Howard