RBYCC...I think I know what you are talking about. I saw that boot today and thought' "Hmmmm...that looks like rubber and could have leaks". I replaced all vacuum lines and rubber tube connectors months ago. Today I cleaned the idle control valve and the tube that comes off the throttle body was cracked where it connects to the valve. I need a new part but was wondering how the heck I would put it on without removing the throttle body assembly. So for now, I cut it, and used a hose clamp to tighten it on and seal any leaks around the neck. Never thought about a smoke test. Good idea. Tonight I got it running better by opening the lambda Clock Wise. I may have had it to lean. We'll see tomorrow how it does on the 45 mile trip in 100 degree weather (It's usually OK when it's cool out except for when it rains...tough to start).