The year should be easy to nail down as it is cast into the heads and intake. First four letters\numbers tell it all. Mine are C4AE-(I forget) F maybe? The C4 part is the year. I was not aware the C3's might not be as good as the C4's. Whats the difference?
Consider this before you get TO excited about the high risers. There not the best design for the 'street', all though I love mine! They do not have an exhaust crossover to heat the intake for better fuel atomization, then again, that means a denser air\fuel charge for max power. The ports are HUGE, not the best thing for lower rpm throttle response. They will support 7800 rpm, but it's unlikey you will turn the motor that high anyway. So why get them? Well, because there rare, very cool, and come with great 'bragging rights'. That said I would bet even the C3's are MORE than you'll likey ever need!
