how many wires on the two upstream 02 sensors
 

1995 blazer, 2dr, 4.3L 4wd.
Concerned with gas mileage at this point.
Brank new plugs, plenty of power but only getting about 10 miles to the gallon. Egr and egr valve port has been cleaned, did a carbon clean on the top half of the egine, oil changed, runs very smooth, shifts great.
Please help
Any suggestions welcome