Replace the lightweight, leak-prone, 1 5/8" OEM up pipes with these heavy-duty 11 gauge 2" Stainless up pipe kit. HD Stainless Bellows that will not crack and leak like OEM. Increase Turbo spool-up and decrease EGTs. This kit is used with twin turbo applications and factory exhaust manifolds or WCFab Duramax Billet Exhaust Manifolds (WCF100363)