bad gas milage

I replaced my head gasket, intake, dist, wires plugs new filters, now I get bad gas milage, about 10 miles to gallon,  does a crossed vac line sound like my prob??? any info will help... thanks,  zeb,   plugs gapped properly, no check ingine light.. my temp is around 190 ... 98 blazier 4.3

Any check engine lights?

Gap on the plugs?

does the exhaust smell strongly of sulfur?? also does it idle rough? check the plugs and see if their fouled out. if the exhaust smells like sulfur and ur plugs r fowling out and u have rough idle along w/ the bad mpg then it might be that the fuel lines in the plenum r bad and leak. this happend to me on my 94 blazer w/ the 4.3.