I am about to do a full transmission service on my wife's 2006 Toyota Sienna 3.3L V6. I will be doing a drain, drop the pan, clean the magnets, replace the strainer & gasket, installing a magnetic drain plug (Toyota's don't come with them) and filling it back up! Also, pulling the cooler line and doing another 8 quarts of OEM Fluid. My question is should I be adding an additive? Lubeguard, etc... I do not know anything about additives please help!