MikeyZ

iTrader: (20)

is there any differences between a 99 ls1 and a 2000 ls1?

Part numbers anything?

Big&Tasty TA

I believe the air pump might be different, not 100% sure.

orangeapeel

iTrader: (18)

I think they are identical.

Starz T/A 17

iTrader: (6)

Yes, the way the air pump hooks up is different since the manifolds were redesigned for 2000+ cars. Although they both have EGR and AIR there are some slight differences. Which is why if you look up headers there are 3 different part numbers for most brands 98 and 99, 2000, and 01 and 02 cars.