[LeanBurn]

Auto transmissions on the highway are no problem for most car built in the past 15 years. Fueleconomy.gov confirms that it is within 1mpg of the manual version. Today's cars are often showing an auto getting better on the highway than a manual. The city mileage is more of an issue but driven conservatively can also net great numbers.

-1.8l H4 engine swap <-(I would save this one for last...$$ and complicated, the car is no spring chicken)
-Higher gear ratio auto trans with auto OD/manual lockup, <--(what about taller tires to test first?)
-exhaust mods (better flow) <--(because at low throttle you need more flow? Most stock systems flow enough for an additional ~40hp, stock is fine)
-minor aero mods, <-----(grill block, front/full belly pan, wheel covers/skirts)
-weight reduction, <-(tough one if you want to retain close to full ability of car)
-lighter wheels, LRR (run flat???) tires, <---(Are the OEM aluminium lighter..try to get to 40psi)
-ScangaugeII or similar (possibly CarChip fleet with wireless download to laptop) <--(I have heard good things about Utragauge as well less$$, worth a search)