Anyone who suggests pulling the manifolds after a seafoaming is not someone I'd take advice from, lol.
I usually put a half can in the oil and the rest in the tank, at oil changes.
It will come out black.
Also, adding a few ounces of trans fluid to the oil after a change swells the rubber seals, and helps with the valve stem seals leaking.
To clean the injectors is not easy, and takes some equipment. I'd look for refurbed ones on ebay.