I really haven't seen any DIY's for Seafoaming S4's, so i decided to make one.
Seafoam is great. I have used it on both my cars and for other motors around my house. It will clean out all of the buildup in your motor and restore power and response. A good rule of thumb to go by is to use a third bottle through the vacuum hose, a third in the oil, and a third through the gas. Now remember this is a cycle, so what goes in, must come out. Now the seafoam going in through the vacuum will be burned off through the combustion so that will be gone, and so will be the seafoam through the gas. But the seafoam you put in your oil will loosen up the sludge buildup and it will just cycle through the oil system unless you expel it (drain your oil). After a seafoam i change my oil, and boy is that old oil BLACK. Also remember, seafoaming commonly will set off your misfire code, so make sure you can clear your check engine light after.
Below will be a step by step guide to properly seafoam your car start to finish.
Ok, first, the easy step. Simply empty a thrid can into your gas tank.
Second, empty a third into your oil.
Now this is the part that actually involves some knowledge. For this step you will need to locate your vacuum hose. I highlighted it below. I have installed a different hose, the stock one should have like a woven cloth look. But still, there are in the same spot.
Now take the vacuum hose and disconnect it from the side that connects to the fuel pressure regulator (circled below).
Now take a cup or bottle and empty a third of seafoam into it. Take the end of dettached hose and insert it into the bottle or cup of seafoam. Run the motor at idle and slurp the seafoam into the vacuum hose (the hose should form a suction). Do not fully submerge the tube, make sure its half air half seafoam.
Once the seafoam is emptied out of the container, turn off the car and let it sit for about fifteen minutes. Then after the time is up run the car at idle and watch the smoke pour out of your exhaust. After about three minutes of idling, feel free rev the motor slightly, as this will release more smoke. After all the smoke has stopped or practically gone, turn the car off and perform a usual oil change to clean out the oil.
The seafoam in your gas will cleanse you fuel lines, and more importantly, your injectors. You can increase the quantities to a half can of seafoam if you really want to, I personally wouldn't go higher than that. I use seafoam on just the oil system before every oil change, it keeps my oil system free of sludge.
Hope this was helpful if you have questions feel free to ask.