please help

i have a 06 tacoma with a 2.4 automatic. i have replaced the tps,fuel filter,cap,rotor,plugs,wires cleaned maf. while driving it would spit and sputter every now and then but now it will run for 2-3 min then once it is warmed up the stumbles bucks carries on cant even drive it. if you stop it will shut off but start back up and idle good for a min or so then act up more. it doesnt matter whether i m going 50mph or going 5mph it just acts like it is running out of fuel or misfiring but the check engine light doesnt come on and over the past year my gas milage has gotten progressively worse. i can hear the fuel pump running. was wondering if anyone has any ideas before going to dealership (http://www.toyotanation.com/forum/showthread.php?t=293028#).
thankyou