Best place to hook up vacuum gauge on 3.9 LZ9?

[niceguy]

Hey guys, I don't have a manual for the vacuum routing but I want to hook up a vacuum gauge to check for possible exhaust restriction. It's drive by wire and it doesn't have a traditional EGR setup. Should I hook into the brake booster hose or is there a better spot? Thanks!

[SappySE107]

You can use an intake vacuum gauge to measure exhaust restriction? As long as you don't use the brakes, the booster port would be ok. I have heard of vacuum ports before and after the cat to determine if its plugged but engine vacuum is used to determine if the intake is restricting the engine comparing max MAP reading vs engine on but not running reading. How does that work to show an exhaust restriction? The intake numbers drop considerably more?

[niceguy]

Hey thanks, yeah you can use a standard vacuum gauge to test restriction at the intake. I was thinking of using the brake booster line but didn't know if there was a better place. I'm only looking to test it in Park, sitting idle. When you increase idle up to around 2-3k rpm, if pressure starts to drop then there's a restriction from what I remember. Now WOT testing is different I believe, where vacuum will increase under a heavy load?

[SappySE107]

Sitting idle won't be a problem then. WOT is for testing intake restriction from what I have been told. I have seen it in action but I don't know if cam timing would be a factor as well. With an angled tube connected to the exhaust, high exhaust flow will create more vacuum. Testing before and after the cat is supposed to be how you can test it for restriction.