My current vacuum pump is a Yellow Jacket 6 cfm two-stage. It is getting old with a shorted cord so I am getting a new one. Does anyone have any suggestions? I do primarily residential. I saw a Robin Air 15800 8 cfm two stage for $225.00. Is anyone familiar with this model? On all of my jobs I use nitrogen before the vacuum to check for leaks. Some contractors I know think it is unnecessary. Any thoughts? Thanks you.