Ok, so I've gone and done it. This is what I want my 91 Camry to look like when it's all done.

http://venus.walagata.com/w/qotsa/new_camry.jpg

Two spoilers going sideways for extra HP, quad exhaust for insane HP boost, kickin' new tires with smokin' rims, and of course the quad exhaust at the top for maximum performance on air conditioning (which will add at least 200 more HP)... for a total of 1,023 HP gained!

but what kind of MPG will she get when done?

At least 200 feet/gallon.