Been doing some research lately as I just bought some new wheels.The lightest wheels that I found that fit our trucks are the Volks TE37's in an 18 inch and weigh 18 lbs .They are forged,super strong and really sweet! If you got the money,the way to go.At a cost of ~ $750 a piece.
Stephanies TE with Volks, Seen them in person and they are the nicest wheels on the forum IMO
The next closest I found are the Konig Countersteer X's and reported weight is 20.5lbs at a cost of $200 a piece. They are a knock off of the Volk TE37X's. That's what I just bought but they are on a limited basis to buy.Two others on the forum have them and got them from the same place .
http://www.toyota-4runner.org/class.../91740-fs-17x8-konig-countersteer-type-x.html
If anybody else knows any lighter ...please chime in!