I've seen guys add it into the brake vacuum line on Youtube. I could probably also add it into the throttle body or other intake inlet. What is the superior method? The aerosol can into the vacuum line would be super easy. Does it ever make any sensors in the intake mad? I have an 86 btw.

Example:

 

There aren't any sensors in the direct flow of the intake or exhaust between the intake air temp and the oxygen sensor..

Follow up question, why do you think you need to do this in the first place?

 

Shaken, not stirred. LOL Anyways I would use on the the three(?) vacuum lines on the throttle body. The brake booster line is too big and you could potentially hydro lock the engine if you give it too much too fast.

 

I can see soot from the exhaust on the ground when it warms up. A portion of the exhaust soot is directed into the intake, thanks to the EGR system, which is still required where I live. It's idling rough and also pinging. A Toyota dealership flushed the fuel system when it idled rough and it did the trick in the past, about 7 years and about 40,000 miles ago. I'm guessing they use Seafoam or a similar product to flush the fuel system. I think I can save about $150 if I do it myself.

 

They instruct users to raise the idle 1,000 rpm above normal to prevent that.

 

The three vacuum tree and the brake booster port are both directly over the cylinder #4 intake runner. I doubt you'd get any Seafoam to cylinders 1 through 3. I'd say your best bet is somehow get it into the intake before the throttle body.