When I had my heat exchanger leak, I had to remove the intake manifold as well. It required an extensive cleaning.
To remove the coolant and Water Wetter that was caked on, I first used some carburetor cleaner, but found it to be an inefficient way of cleaning. There wasn't enough force to spray it all off. It also killed two square feet of grass where I sprayed.
My outdoor faucet has a hot and cold outlet, so I sprayed the aluminum intake manifold with water. I was amazed that it cleaned off in a couple minutes with the hot and forceful water.
Also, the intake ports near the firewall were caked as well. I used a wooden stick and shop towels to clean it all off as best I could. I wasn't too concerned about it at the time. A friend suggested a tank or two of gas and that area would be cleaned off anyway from the fuel. Despite what others said during my quest for information, it doesn't seem like there's any logical way for the coolant to damage the injector.
Art Whipple also suggested I spray some WD-40 in the ports and turn the engine over to eject any loose particles. I'm not sure how much of the material in that area is steel vs. aluminum, but either way, you'll have a long wait for the parts to return to you from the states, so I would suggest it as well.
Art also sent me two new injectors. In hindsight, I should have just requested eight new ones. I put together a parts list of everything I thought I deserved, and they sent it all. Don't forget to order a new intake manifold gasket if you take the intake manifold out to clean it off.
With my experience, I searched for a way to clean the injectors as well. Most information lead me to the conclusion that the only way to test and clean a fuel injector is to send them to a facility that has the equipment to do so. I chose not to use the in tank injector additives. Despite what others have said, it doesn't seem logical that coolant would damage the injectors. Injectors build up deposits and become blocked by small particles that make it past the fuel filter. I just don't believe that coolant would do anything besides cake up the area around the injector.
