So wait a minute...you removed the muffler and the cats and are now complaining that the car is loud? Put the bastard back in and problem solved.
As far as your question goes, I'm not sure. Would the vacuum be enough to open close both lines? Also, the amount of backpressure might be too much.
As far as your question goes, I'm not sure. Would the vacuum be enough to open close both lines? Also, the amount of backpressure might be too much.