i have used seafoam now twice in my car... just turned 150k miles last week. Used it once around 120k, and again today ~150k. Both times I fed it in through the brake booster line (R side of engine, PM me for pics). Although the can says only use 1/3, i slowly feed in the entire can, letting the engine stall out on the last little bit by submersing the hose directly into the seafoam. Let it sit for about 15 minutes--- start it up and watch the smoke! I wouldnt recommend driving anywhere for at least a few minutes, as the car tends to stall when no gas is applied (ie- stoplights, stop signs, etc).
It got rid of my rough idle, and seems to make the car run smoother overall. Hey, for only $8, its worth it to me. Not sure about MPG improvements or whatnot, i have never tested it out. 3rd gen 4runner is never gonna get the kind of gas mileage id like anyways.
ps- i went to ace hardware and bought a clear plastic tube to use as a "vacuum" line to suck the seafoam up. Not sure the implications of sucking it directly into the real brake booster line, but i thought id rather be safe than sorry. hope this helps