Can anyone tell me why there would be a difference in headers from 4WD vs 2WD? I have an 00 Tundra AC 4x4 v8. Getting the new frame and would like to replace the manifolds at the same time. I like the Gibsons (603) line, but they say not available for 4wd? Not sure what the difference would be. I also like the price of the Pacesetters Armour Coated shorty's, but do not know how well they are made. Anyone install these and can vouch for them? I would like to get something with a lifetime warranty and so far only have found Gibson offers that. I'm open to other suggestions of good quality OE replacement headers. Any info is appreciated. Thanks!