You are working on a throttle-by-wire system that put Toyota in the news a few years ago. Most independent mechanics do not want to work on them for fear of becoming party to any future lawsuits. Most likely the new throttle body assembly needs to be programmed to the vehicle by the dealer. No throttle response is a very common symptom, but I have never heard of one going to wide-open-throttle related to the brakes. Seems like a pretty dangerous condition. I have a suspicion that is another symptom related to what set the fault code.
Can you get to the throttle position sensor to take some voltage readings? To be valid, they will need to be taken while it is plugged in, by back-probing next to the wires where they go into the connector.
Thursday, June 29th, 2017 AT 4:38 PM