[cowmeat]

Nah, at 45 mph I average way over 100 mpg on the FCD, and even at 65-70 mph I'm averaging over 75 mph on the FCD. If I'm following a truck on the highway I'll get 80 mpg at 75 mph. You still definitely have an issue, unless the cross wind is always there where you live, since that will automatically rob you of mpg.

If it's bucking at low load I would replace the EGR valve (seeing how old and crusty it looks in the pic). You might want to also check all the ground straps, the 12V battery, and throw a new PCV valve on it. Pop the IMA cover off and click off the big battery (or install a clutch switch) and see what it does then, in case it's background charging while you're on the road. Torque the plugs to OEM specs. Other than the EGR valve those are all cheap/free checks. I always start with free, then cheap fixes when I'm doing guesswork.

If it's out of alignment or the brakes are dragging it will rob you of power. Loose under panels or body parts could do that if they're catching the wind at speed. AC clutch, tensioner pulley, etc . . . can bind up, although those usually make some noise as a warning. Bad plugs, wires or coils, fuel pressure . . . . the list goes on and on!