What is wrong with my engine? '05 Ford Focus SE ZX4

I didn't mention in my original question that the problem doesn't occur until the engine is warmed up. Also I do not get a check engine light. Would this make any difference to your response?

The symptoms you posted are indicative of a vacuum leak or vacuum leaks - 'engine warm' .. The most common source of the vacuum leak(s) can be found within the PCV valve 'system' .. This is based on what we commonly see at the shop with these vehicles ... Hands-on testing is required. Again - best to use OEM parts .. Some aftermarket PVC valves have the wrong internal spring and can cause more problems! .. All PCV system hoses and the valve should be replaced.

Thanks. Started my '85 Dodge 600 to go get parts for Focus and my break pedal went to the floor. Makes a loud whooshing sound at pedal when depressed. No fluid leak. Master cylinder full. Bad Master cylinder? I'm running out of cars!!

Master cylinder is first suspect .. Get you a rabbits foot - 4 leaf clover or something too while you're at it .. Crap!

Thanks for your input. Painstaking repair on the Focus. Lotsa cuts & bruises! Thank you Ford designers!!!!!