[BruceH]

Look over the engine bay closely. All around the intake manifold and there is one that hooks up to the brakes. Make sure every line is hooked up on both ends.
The reason I suggest it is because my car acted very similar after I changed my clutch. It turned out the brake assist vacuum line had come off when I was jacking the motor up and down. Plugged it in and presto, car back to normal.
I hope it's that easy for you. Keep us posted.