I don't want to give you the wrong info but I used the vacuum line that ran to my brake booster. Thats what a mechanic friend of mine suggested but it wasn't for the 4cylinder. Can't imagine it would be any different though.
I used the same one for some BG44k on my 4 cyl a while back,
Here's a few pics but make sure you feed it in slow, don't let the engine stall.
Just wondering how that worked for you I ask because I see the line you used is right above the 2nd cylinder port looks to me like the line that comes off of the top at the throttle body valve would be a better location to get the sea-foam or what ever you use to all 4 cylinders instead of just the first 2
just my observation but I have done this kind of thing only on older carborated motors so you just dump it straight down the carb.
"Pour it in till it stalls?" Sure sounds like a recipe for a hydrolock!
"Pour it in till it stalls?" Sure sounds like a recipe for a hydrolock!