location of pass. air check valve

I'm sure someone might chime in with exact ,, but ... Look
Up shoebox . Go to his main page . He has diagrams for just about everything you might need . Sorry I couldn't help more .
Don

just checked on his site, unless Im mistaken, he mainly deals with the LT1 and 93-97 Fbody, not 98+.

Try the 4th gen parts books, available to download in the sticky threads of this section. They should have a exploded diagram of what you need.

Also located in the regular threads of this section, you will find the factory service manual for your car. Look for thread titled "GM service manuals".

They are on the pipes going to the exhaust manifolds on each side. You can't miss them. I take them off to change the plugs cause they are in the way.

Sorry I wasn't more help . Looks like got ya going in right direction now .
Don