I am not sure how well seafoam would work on it...
The deposits are caked on the valve stems and seats. You would need to soak them well in order to dissolve them.
I could think of spraying solvent through MAP sensor opening aiming towards each valve.
Do it on cold engine. Let it soak, spray more.
Then, using a syringe and some type of small gauge (large diameter) needle suck it out. Spray again and maybe do it like 2-3 times.
Starting the car might be problematic at this point as you will not be able to pull everything out.
Eventually, to help it more, you can remove spark plugs, pull fuse from injectors, and crank it a few times after you are done.
Or pull the fuel pump relay before you shut it down so that pressure drops in the line and no fuel will be dumped during start.
Spraying seafoam just into the intake will not really make much of it as the deposits are too hard.
Both in the gas tank.
I use and have a close system fuel injection cleaner setup that runs the car on a compress can of cleaner that you buy over-the-counter (Ecklin)
I find that the in-tank products are ( just fine for me) but you may need something more.
I have took off the intake manifold to clean the intake valves at 125k miles using a can of B12 Chemicol at Walmart for $3. I am not good at documenting. I can perhaps took pictures of the tools I use to clean it with. My car now drives like new again..
I would rate it harder than a brake job.
First you deal with a few wires and sensors. Then you have the gasket and assembly - all must be neat clean.
It is not hard as tricky, it is hard as attention to details to not miss anything and reconnect all of them.