Can someone tell me the part i need for a 2007 Silverado, 4WD Crew Cab? I ordered what i thought was the correct part....AC Delco 214-2149 and it only had one port whereas the one i have on the truck now has two and is slightly smaller. I'm not very mechanically inclined but can change this out once i know i have the correct part to work with. thanks much. great site and info here.