Carb problems

I am having problems with 8.5 mpg. Also my car will just cutout sometimes and die after it is warmed up. I have a 71 duster with a 30 overbored 360, kb107 hyper pistons, moly file fit rings, stock 308 heads, eddy rpm air gap, eddy 600 cfm manual choke mechanical sec's, new volt reg., new water pump and dist, carter fuel pump, new hv oil pump and pickup. The block was cleaned and magnafluxed. Rebuilt with new bearings and plugs, crank regrind and rods, and then balanced. It also has a a-230 3spd manual with 8 3/4 rear end w/ 3.23 open diff.
The car has since been changed to 2 stages lean on both the cruise and power mode. The problems with the cutting out started then but not the mpg. Never have i had wet plugs and i got about 3000 on the new motor. also the motor is a 1990 and has a stock hyd roller cam and lifters. any help will be appreciated.