I think the decarbon procedure is for the insides of the combustion chamber if I'm not mistaken. For that I would think that the ford stuff might bee the best solution, I looked down into my combustion camber today while replacing my plugs and putting a new intake manifold gasket on. I would stand to gainsomething from the decarbon proceedure I'm sure, but I can't tell how really bad it is in there.
Your best bet to make a huge difference is to pull your intake off, and clean all the years of crap outta it. I did this 2 days ago, and in the process I noticed that my gaskets were kinda shot for whatever reason. well off the intake came today and 2 new gaskets went in. I spent about 3 hours cleaning the mating surfaces of all the dirt and bits of gasket. You have to work slow around the intake ports so you don't drop stuff down inside them. with the new gaskets in place I really got to see how much room there is for me to port the heads in the future. I'm betting that I'll get 5-10% more/better airflow. Anyhow back to the task.
I highly reccomend taking the intake off and cleaning the crap out. I used 6 cans of Berryman's B12, and they are spotless. I would say that you might want to start the car for about 2 min before you pull the intake off just so a little heat might make the gasket a little pliable. Mine cracked and stuck I think cause it was 30 degrees outside or so. If you do take the intake off, make sure you clean the head too, a toothbrush with some B12 sprayed on it works nice. Also don't let tooooo much b12 get into the combustion chamber. I did and it was a pain to get the car to start and then it ran like crap. after a few min it got much better. With a new gasket and all sorts of clean inside I have to believe it was worth the time and little frustration.
If you end up doing the "decarbon proceedure" let me know. I'd be interested to hear how it goes.