It's obviously opening and working or the problems wouldn't go away with the vacuum line plugged.

Most exhaust shops can check the back pressure. They drill a small hole in the pipe ahead of the converter and check the pressure with a gauge. Then weld up the hole when done. Many do it for free.

 

The EGR is fine. But I have those issues when it is plugged in and I don't when i plugged up the vacuum line to the EGR. And if I suck on the hose to the EGR while it is idling, it dies.

 

thanks lxman1...I will check with a local exhaust shop.