Were you having problems after replacing the front motor mount. If so check the air flow assembly from the air filter to the center of engine. If it has any holes or small rips it should be replaced. Look very closely at the rounded section while (moving it!) around. If you notice tears or rips it maybe letting eccess air into you intake affecting you response. If it has to be replaced it is a toyota parts containing the same number as the lexus part, but cost less money. Call around to toyota dealerships to get the best price. One other thing I tied a plastic bag around the ripped section, make sure it doesn't get burned or caught up on anything. Take your car around the block, you should instantly know the deal. car jerking at start offs, slow speeds and in lower gears almost certainly denotes motor mounts.