It may be lighter, but i ran with either a soft top or no top, and doors without windows or no doors, and no tailgate, and the best i could get was 18mpg.
Throw everything back in? 23mpg.
There is SO much more wind drag with the roof off, it does accelerate faster tho (and chirp the tires on every turn...

89 4Runner
3" BL, M/T locks, 33"bfg mt, bilstein, Kayline, tubebumper, toyotafiberglass panels
TBI: Elocker,3.4 w/ORS,b+b,S2Sstg2cams,arias pistons,P+P intake,TRDs/c,URDpullies+7th,downey headers,MAPECU2,WEGO WB, SupraMAF,walboro255,stg4clutch, EPaOo2 sim