I did mine off the brake booster line. The car could barely idle with it off. It made a huge difference on idle and the powerband. The brakes felt a little spongy for the first minute or so after reconnecting the line. I suggest two people do it, so one can modulate throttle, around 1500-2000rpm to get smooth coverage while the other uses the hose to suck up the seafoam. After that I shut the car off for 5 minutes, then fired it up and got no smoke at first, then I goosed the throttle to smoke out the neighbors, so I went for a little drive away from the house lol.
We did this about six months ago, and actually used this write up because I couldn't find a better location closest to the TB that would allow the seafoam to hit all four cylinders evenly. I basically wanted to see if others used the brake booster line like I wanted to. Only took like 6 months for me to actually join the bopard and start posting haha.