I have a 2003 Toyota Tacoma with the 2.7 four banger.I am having a problem with carbon build-up in the combustion area.I took it back to the dealer 8000 miles ago and they decarboned it.It was fine for about 4000 miles,but now it is back.I would like to Seafoam or water decarb but I am unsure of where to introduce the liquid.Any ideas?Please do not tell me to use Fuel Power as I developed this problem after usig it for 13000 miles at the rate of 1 ounce to 5 gallons of fuel.Thanks