My Volvo 122S (wagon) was getting about 20 city/25 highway with the B18 that was all stock except for the Weber progressive two-barrel. My best tank on the highway with the carb was 27 mpg. I recently megasquirted it with a GM single barrel TBI and it's now getting much better mileage, about 22/30. My new best tank with the injection is 35 mpg. Pretty dang good for a 40+ year old station wagon! I think the tune is getting dialed in well enough that I will probably put a catalytic converter on it, too...I'm running at stoich all the time and a cat is only $50, might as well save the world while cruising in my classic. 
Bryce
Portland, OR | '69 Bug | '05 Saabaru | '95 Impreza | '67 122S | '07 Sky Redline | $2009 West Coast - AWD Fiero Hybrid