01 taurus pushrod motor. Vulcan? Today it started idling poor/ stalling. I can hear a popping sound from muffler. Almost like a coffee percolator. No codes. Motor seems quiet. No odd noises or metallic sounds. Friend says burnt valve? Last week or so I thought I heard exhaust drone on acceleration. Almost like a hole in muffler. But muffler is good, same as exhaust pipes. The perc sound is not rhythmic. Sort of uneven. Like a chugging/ puffing sound. Intake manifold leak? Upper/lower? This year does not have IMT. Intake tuner device?
Well, PCV intake elbow is split
Good find, I was thinking loos baffles in the exhaust system!
Nice work!
Buy yourself a beer on me! 
The 2004+ Vulcan motor has the intake valve but many online sites say check the intake for leaks and all hoses and fittings. I took off the elbow and saw the big tear but thought I did it by twisting it off. No matter, a tear is a tear. Car idles fine now