You could chuck a K&N filter at it, some Iridium spark plugs & maybe a high flow back box. You might net 5-10hp but it should make it rev a bit more freely & use a little less gas. I wouldn't bother with much more than that with the 1GFE. If you can't make it go like a sports car you can at least make it handle like one. Lower it, strut braces & stiffer rear sway bars should keep you happy on the B roads for a while.