My dad's 05 Tundra 4.7 2wd has this issue between 2k and 3k rpm cruising or medium throttle on takeoff where he loses power intermittently, it feels like you're slightly letting of the gas, then getting back on it quickly and rhythmicly. It happens about every 3 seconds. On our scanner you can see the short term fuel trims and the upstream O2 sensor readings match the problem, you can see the readings go positive then negative in rhythm with the problem. We have cleaned the throttle, replaced the MAF, replaced spark plugs and coils, replaced the air filter, put in fuel cleaner, replaced O2 sensors, and we are about to replace the fuel injectors. So far none of these things have changed it slightly, we are holding out hope for the fuel injectors but it's looking pretty grim. We don't know where to go from here.