..this is an obvious statement, but this thread shows just how much they hurt.
http://forums.corvetteforum.com/show...6+wheel+weight
In summary, 17" stock wheel weighs about 16.5 pounds less than 18" chrome wheel.
17" stock wheel dynoed 12rwhp more and 9rwtq more than heavy 18" chrome.
Now imagine how much better a 16" lightweight wheel would benefit..