If u have a GTP then what do u mean the plastic manifolds on supercharged models as well? GTP's come from the factory supercharged so therefore your supercharged as well my friend. The 1997-2003 L36 equipped GT's have a plastic upper intake manifold and some of the 04's and possibly 05's also. I could be mistaken so somebody correct me if im wrong. The L26 model blocks have an aluminum upper intake manifold. But for your EGR, honestly ud be better off just buying another EGR unit from a junkyard if u dont want to pay all that much for a new one from a parts store or just scrap it. I scrapped mine due to installing an intercooler, and havent noticed any loss of performance or anything. Where u live u might have to have it for emissions of some sort. I dont know, just tryin to help. up here in South Dakota there are no emissions or anything so i dont know to much about all that non sense. lol.