3 weeks ago when i was driving on highway RT22 in pa happen to run over a big rock in the middle of the highway, and the panel with that filter broke off and got replace because, it was hanging. After that night my 07 IS 250 awd started move completely slow as in i would have to be flooring the gas pedal to get some form of speed going. need to have a idea of what i'm dealing with here before i go spend money on what can be simple problem.

 

It can be a simple problem or a huge problem. You need to put it on a lift it and inspect the whole bottom half of the car. You could had damage more then just the bottom half of the engine cover.

 

What panel with what filter? Take some pics.