sputting and shaking

I have a 2000 gt and I just cleaned my engin bay with a preasure washer and motor degreaser. Now I drive the car and at low rpms, the car sputs, jerks, and shakes until it reaches 2000 rpms. This happens throughout all the gears. The only modifications are a mac cold air intake, bbk offroad x-pipe, and flowmaster cat back. I tried disconnecting the egr valve and plugging the tube and it only seemed to make thing worse. Please help, thank you!

new problem charateristics

If i drive normal, the extreem shaking goes away at 2000 rpms. When i drive heavy, the crazy vibration goes away above 3000 rpms and then the car gets a sudden boost in power and takes off. But getting to 3000 rpms takes a long shaky time. I think there might be an injector or some kind of fuel problem. And at idle, it very, very slighty surges. Thanks again for your help!