upper intake -> lower intake -> head porting will wake it up a lot, combined that with some nice equal length headers and a low restriction exhaust, more aggressive high rpm cam, maincap girdle in the bottom end.
then, if you're feeling ballsy, get a standalone programmable engine control computer, 200hp without boost wouldn't be out of the question with the right work.
if you're going to convert to maf, find one that doesn't suck, ranger Maf sensors just plain ****in blow, huge intake obstruction.
if you feel like learning a lot about engines, run a map based standalone and you'll make better power, might not make better fuel economy though.
edit: @adsm, if the 2.9 was 'pretty well maxed' from the factory, why do the european models of the exact same engine have 20-30 more horsepower on the exact same internals?