Don't overfill/"top off" your gas tank when you fill up. Stop at the first click. Topping off causes excess fuel to enter the charcoal canister and hastens its demise. If you are not the original owner of your Pathfinder, perhaps the previous owner practiced this and ended up killing the charcoal canister.
What is the bulletin number of the TSB your mechanic supplied? What is the exact engine code? The code in your thread's title is incomprehensible. P1446, maybe?
Don't bother using Seafoam, all it is is:
40 - 60% pale oil as a carrier and light lubricant
25 - 35% naptha, a solvent
10 - 20% IPA (isopropyl alcohol) - a solvent and octane booster when used in the gas, which is why some claim a performance increase when using Seafoam, until the next tank without the added IPA!
The white plume of smoke generated by Seafoam when ingested via a vacuum line is the pale oil burning up. Carbon generates brown smoke when burning, which is why you sometimes see clouds of brown smoke emanating from other vehicles on a highway on-ramp during high load for example; if one drives like a grandma, faster carbon build up can result and a high load can purge some build up. Pale oil also coats the catalytic converter and oxygen sensors, which can impact the sensor's ability to sense and the catalytic converter's, well, catalysing ability. Use a fuel system cleaner containing polyether amines, which is proven to clean deposits without leaving behind its own residue (
SAE paper detailing PEA). Products which are known to contain PEA are Chevron Techron, Gumout Regane, and Redline SI-1.
Engine oil blenders spend millions of dollars in research and development to generate a formulation of oil that is designed to meet API requirements and to do the best job lubricating and protecting your engine. Why throw in some harsh solvent such as Seafoam or other snake oil to upset that formulation? If you keep up with oil changes, you should not have any sludge to worry about in the crankcase, and do not require Seafoam or
any oil additives for that matter.
As for top-end cleaning, use a product designed for such a task such as Mopar Combustion Chamber Cleaner or Amsoil Power Foam.