just throwing this out there to play devils advocate...
seafoam CAN go wrong. if your engine has never had the seafoam treatment before and you are at a higher mileage, there are risks involved. this mostly applies to engine's that have been neglected in terms of oil changes, among other things.
sometimes, the gunk and that builds up in your engine "assists" in keeping worn, sloppy parts within tolerance as they wear down. additionally if you have ALOT of build-up, its going to knock those loose and send them through the rest of the engine. the last thing you want is a chunk getting sent through your valves or put you on the way to a spun bearing.
seafoam is a great product. i am as american as it gets, but the japanese do 4 wheels and a motor the right way (and 2 wheels and a motor), point being that the majority of horror stories are from american vehicles where gm, ford etc. are WORKING to get 200 hp out of say a V6 and thus the engine is quite a bit more stressed, whereas toyota easily got 250 hp and tuned it down to 200 hp for the longevity of the engine (just an example).
(this also applies to things like transmissions where the crud build up after x amount of miles is actually "helping" the transmission (really just masking the problem) and thus a full flush isn't good.)
basically, its a yota and it'll love seafoam 97% of the time. i just want everyone to be aware there is a possibility for a negative outcome.
1996 Mustang GT Bad Seafoam Results - YouTube
jus' sayin.