I believe it's a module that hooks up to the coolant temp wiring. Basically sends a diff signal to the PCM. Modifying the fuel amount to 'increase performance'.
It's a gforce performance chip... Aka: waste of money. Get rid of it. The factory ecu's cannot be tuned or adjusted. Most likely that thing is causing you to run lean. Get rid of it ASAP. Toyota designed these engines very well and trying to modify the fuel map on a stock engine is not a good idea.
i would get rid of it. it doesnt mater what you do to the sensors before it enters the engine. a toyota field rep told me that the ecu will use the o2 sensor readings to correct any mods you did before it. even if its lying to the computer that there is more air going in the o2 will still see that its not and adjust accordingly