Well I think I found the issue. Yesterday I replaced the purge valve (I think. I replaced the valve and hoses on the hose coming off of the intake maifold going to the charcoal canister)with the one off my parts car. After driving it a bit it didnt really seem to change anything. So I started thinking, when we replaced the engine we werent really sure which plug went to which O2 sensor, so we guessed. Well some of the issues I have been having could be related to that, so I switched the plugs around. I now have about 40 miles on it and the gas gauge hasnt dropped below the full mark yet. For the past month it would already be at 7/8ths of a tank by the time I got to work after filling up. So I think I fixed the issue. My neighbor "the Master Mechanic" said that couldnt be it because it wasnt throwing O2 codes. I dont think it would have because the O2 sensors were working just fine, they were just sending data from the wrong place in the exhaust system.

Sound right to anyone else? All I know is it seems to be running much better, power(well respectively) on acceleration, mpg's seems better though I wont know till I put more miles on.