P0440 engine code

Engine Mechanical problem 6 cyl Front Wheel Drive Automatic 61xxx miles

My check engine soon light has been on for a couple weeks. I have a 0440 trouble code. Generally That means a bad gas cap. I've replaced the cap with two others. Then I had the car re-scanned. Still have P0440 code. I've also checked both hoses connected to the EVAP canister, and it seems to be working. It was suggested I take carb cleaner and spray it around my vacuum lines and listen for the engine to rev, thus detecting a vacuum leak. NOTHING. When under the hood, I manually accelerated the engine at the throttle body, and the engine hesitated, almost died, and then recovered. It does the same at the accelerator pedal. HELP!