Who has done this? I'm thinking about doing it. Since it cleans the junk out the engine and such, would going to synth oil be a bad idea? Or doe it even matter?

check this page out
http://my6thgen.org/showthread.php?t=253&highlight=foam

Dont have a username and password for that site?

Yes, give the seafoam a shot. Warning: It will be smoking all over the place and your neighbors will think your car is on fire and call the fire department. Seafoam is a great product, I recommend it to everyone.

Boating guys love Seafoam to get carbon out of their 2-stroke combustion chambers.
I use it in all my cars every 3 or 4 tanks.

Is it really made of foam from the sea?

I need to post 12 more times so I can start my own thread...

i do it on all my cars every 6months, works wonders with removing carbon build up

I ran it through my max, and a few days later it developed a dead spot at 188 rpm. I unplugged the TPS and it runs normally but idles way high. Replaced TPS twice and knock sensor with no change. Anyone ever encounter this problem or know how to fix it? Thx

Old tread...New user.... I have used Seafoam for 15+ years with only positive results!