rxbahamut

I have been reading around and seen many of the 1st generation carburated engines get 21 city and 30 high way and when it went to the 13b fuel injected it went to 16 city 23 high way. I always thought that fuel injected engines were more efficient. First is this true? and Why is the fuel injection worse? I have tinkered with switching old jeeps from carburetter to fuel injection and they get better mileage in the end. So I wanted to ask the RX7 gurus and find out why.