U will be very lucky to produce 220-240rwhp without going turbo or even itbs. xdreamer from supraforums has got 225rwhp and the guy has done most possible bolt-ons inc secret mods such as egr mods,fuel mods and coolant bypass mod. To be honest i think all these so called chips are crap. U mite as well get an safc and dyno tune ur car. If you wana learn more about NA supras, then the best place is supraforums. The majority of them have gone turbo because bolt-ons are just so expensive and u dont get that much of a gain.
Have a look at this page. its a basic guide to modding ur na
http://www.supraforums.com/forum/showthread.php?s=&threadid=148908