for hp,
1. K&N drop in air filter - $40, possible little more hp & mpg, biggest thing is it is reusable (great if you find yourself in dirt a lot
2. K&N intake - about $300 with claimed 5-10+ hp plus a little better milage
3. Flowmaster 40 series muffler - $140 installed, few more hp and about 1-2+ mpg (plus best sounding muffler for the FJC)
4. unichip w/pda power display - about $1100, on a 2004 stock tundra the unichip gained 16.4hp and 21.5 lb.ft. of torque @ 4000rpm. they carry it and have a lot of info
HERE AT PERFORMANCEPRODUCTS.COM
5. URD supercharger - $5000 + install - said, but not prooven to take your FJC from 239hp all the way to between 340 and 380!!!!!
HERE is their website where you can find all the info and even buy it.
hope that helps
-mike