Hey guys, I have read a bunch (not all) of the intake questions and different opinions about what intake to upgrade to and whether or not they even produce horsepower gains that are worth the investment. So I decided to do some experimenting of my own and report back to everyone. The results are in and you can put together an intake system that produces between 5 and 10 HP/torque for about $100-$120. Here's the skinny.
My truck is an 01 2RZ (2.4L). I already had a K and N filter installed, dynomax super turbo muffler, doug thorley headers and LCE underdrive crank pulley. Upon dynoing the vehicle with these mods, the truck produced 131 horsepower and 144 torque.
Stock air box pulls cooler air from the fender well so left it alone. Kept k and n filter in it. Purchased a spectre intake tube (goes form filter housing to intake) from Autozone which is designed for acura/honda but fits this system almost perfect. Also purchased 1 silicone coupler and another piece of longer rubber 3" hose to connect everything. Tube and piping cost about $60.
Had truck run on Dyno again. This time HP was 136 and Torque 151! Just by eliminating the factory piping! I will say that the truck was ran on dyno after it had cooled down and with a fan this time. The first run produced slightly less gain.
Conclusion- By adding k and n filter to factory air cleaner box and replacing factory intake piping with a smooth, straight tube you can expect a 5-10 hp/torque gain...and all together I spent between $100 and $120 (don't remember exact price of k and n filter)