I know Sal of PSP talked about it once, if I remember correctly it was changed when they improved the Intercooler.
So I'm going to say 99 + 2000 have the orig style, and 01 and newer have the newest style. As for performance it seems
a 99/00 with the same Mods RUNS JUST AS GOOD AS ALL OF US.
But I was told the new Design was SUPPOSE to be improved performance,
BUT CANT SAY FOR SURE....
I also remember one of the turnners saying that you get better performance numbers with the runners and also the volume of the intake is bigger to.
I think runners and velocity stacks are suposed to help out low and mid RPM range by straightning out the air a bit.
That and the different bolt pattern on the later years along with the bigger mass air flow and stronger webs, more plug threads are some of the factor's that made me decide to upgrade form 99 to 04 even though I don't race.