This is not something for a do-it-yourselfer to monkey with. It's the same system that put Toyota in the news. The throttle body is the least likely thing to cause a problem unless what you replaced also had the motor and position sensor on it. There will be a diagnostic fault code stored to indicate the problem. A scanner is needed to access that computer and to read the code(s). If a problem develops that leads to loss of control, you want the dealer and manufacturer to be parties to the lawsuit, not you.
August, 31, 2011 AT 8:08 PM
You're likely having a problem with one of the dual TPS sensor incorporated into the electronic throttle body. When it has a problem with one, it defaults to half throttle. If it has a problem with both, it shuts off the throttle completely. Like Doc says, get a diagnostic done by a shop that has experience with "drive by wire" systems.