Originally Posted by Joboo
Besides codes, should I notice any change in performance when removing and plugging vacuum lines?
Since the removal of any vacuum line will admit air into the intake that has not been accounted for by the MAF sensor, you should produce a condition lean enough to cause a stall or low idle.
You should be plugging the vacant intake port, not the line, initially. If you plug the port and the idle improves, examine the fitting, hard plastic line and any other solenoids or valves in the path for leaks.
Another thought: Also check your EGR valve is closing and seating properly. If you apply vacuum to the fitting at the top and release you should hear an audible clunk. Not a definitive test, but at least tells you the spring loaded internal plate is moving. You could also try blocking the EGR intake port entirely.