Tbi without oxygen sensor

Hi everybody

I own a 92 Blazer 6V 190 3.1 TBI 2WD
I live in mexico, so the truck is mexican
it's 150 000 miles
Its mileage is excesively low 9 MPG.
I was thinking in a oxygen sensor change, but i just wonder it hasn't!!
The tires alineation is ok, it is 3" lifted
I recently tune it up in greasy monkey
I'm not using the AC

Any of you can tell me how the injector feedback is performed without the sensor? and How can I improve the gas consuption?

Changing your fuel filter is a start. Anything else it could be a number of various problems. But I'd start with a new fuel filter.