Intake maifold PN# has me stumped
 

12560688....that is the # cast into the manifold that I have, NO-ONE has been able to tell me what this came off of and the only reference I have been able to find is on NHRA's tech spec web site relating to allowable parts for the '00 Chevrolet/Pontiac engines, and GM has been no help because they have NO part that matches that # !!
The circumstances behind me recieving this manifold were kinda strange too, I didn't explain it in my other post but a friend of mine bought it off of ebay day before yesterday (he hasn't even recieved it yet), he realized it was an LS1 manifold after he had bid on it so he decided to give it to me as a late birthday present (only a month late), he said that the guy he bought it from used it on a flowbench to test LS1 head porting with a stock manfold

is this some kind of race-only manifold or a flow-bench only manifold ??

here is a picture of it....
https://i21.ebayimg.com/03/i/00/b0/b0/3f_1.JPG

I also posted this in Internal Engine...sorry for the double post......I normally NEVER double post but I REALLY need an answer

Re: Intake maifold PN# has me stumped
 

Since it has EGR provisions, I'd say its from a fbody.

Re: Intake maifold PN# has me stumped
 

I have that same manifold..its on a 2000 ws6 trans am ls1 intake