Are you talking about the EGR valve on the early trucks? 99-01 i believe. All it does is dirty up your intake, not robbing you of any power. But i wouldn't bother with it unless your installing headers, since you'll need a block off plate for factory manifolds and a tune to get rid of the code. unblolt it, block hole in side of you intake (Google or ebay "LS1 Intake EGR block off"), and block hole on manifold (LS1 Exhaust Block Off Plate) or buy headers without hole. Then get a tune to make code go away.
