Yep i do about the same, in my 3.4 auto, best i've gotten was 20.5 mpg (usually around 19.5)
My auto 3.4 is about the same 0-60 as my 3.0 89' 5spd. (when on stock tires). the 3.4 will kill it over 60mph however.
My bud has a 3.0/auto in his pickup... it's SLOW.... (compared to my 3.4 auto or 3.0 5spd) but it gets him from A to B....

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