Ok this is what I am making out of this and I am sure Sven will correct me if I real far off.
He is going through the basic of EFI, starting with the basic of the internal combustion process.
He talks about the pressure starting with atmospheric 14.7 psi nominal, goes into how the lower displacement of the cylinder (down stroke or intake) will pull in the air through the intake and how that air gets mixed in properly with the fuel.
If you have air, fuel and a source of ignition (spark) or if you are talking diesel (heat from compression), you will have fire. Now the key is to have that fire in the most efficient form, thus the proper air-fuel ratio.
Since the engine operates at different speeds as well as in different environments, the A/F ration varies. Be it from less barometric pressure (or more) or as the engine speeds varies. Since there is a time factor for the fuel to ignite and give complete combustion, due to cylinder speed, the start of the ignition has to be right for most efficient power.
Due to the gas laws, as well as various other factors such as the flame front, burn time, etc, the timing needs to vary.
On the old fashion Point systems, this was accomplished using advance be it from vacuum or centrifugal weights or combination of both. Anyone that every messed with the old Mallory Dual Points distributors and made all the little adjustment for ignition curves can understand such.
With the EFI, all this is still being taken into account, but uses sensor and electronic for the most part to accomplish the same thing.
Bottom line the sensor provide information to the ECM (or whatever controls the ignition and fuel injectors) to insure that the fuel is injected at the right time and the spark is fired at the right time to make it all come together for the most efficient burn for the condition at that time.
The sensor sense various information be it pressure, o2 level, rpm, etc and converts all to electronic signals which are analyzed and then proper electronics signals are sent to the FI and the Spark to make it happen right.
Much of the information he is provided is detail on how the sensor operated and feed info in and out of the ECM to get the proper timing and fuel ratio. Since a good portion of this involves sensor and those sensor send electronic information, it appears that he is getting in to the detail of such. This would involve the various milliamps/voltage and what signals are being sensed.
Good stuff IMHO but much more detail that the typical owner is familiar with or would want to know. That said, knowing such and having a basic idea of how all this comes together and is used to insure that the spark ignites the proper fuel ratio at the right time and adjust these as things change can help one troubleshoot the EFI. Basically something at ideal require a much different timing than something at say 5000 rpm as well as change of fuel amounts due to amount of air from various situation.
With a carb, things are pretty simple, the air gets pulled through the venturi of the carb, the fuel gets suck into that air stream, gets mixed and get ignited. Since it is based on gas laws and physic, we try to meet the idea situation through the use of jets (to have close to proper a/f ration) to correlate with the air flow. Since the air/flow will vary depending on not only the crank speed, but also atmosphere (thus the need to re-jet at higher elevation or lower), but also the intake design as well as the exhaust. The exhaust plays a big part due to the gas flowing out of the cylinder and having some overlap with the intake and due to the gas laws, the better the exhaust can scavenge the cylinder, the better fresh air can fill the cylinder, not only in quality, but quantity too. Still all these are fixed and try to get the idea middle ground for the most part. The only item that is variable is the spark which can be changed via advance curves (well on some carb like the old predator, it did adjust more for the a/f than say a Holley Dominator).
With EFI all these variable are changing more and are based on real time information from various sensor. Much more accurate when right as well as efficient and more variable for the situation, thus in some the ability to learn and adjust for the engine and conditions. Knowing how it all works and what the various sensors do, and how they work, and how such information is used to make the needed adjustment, can go a long way to troubleshooting as well as make the proper set up.
One thing I will throw in, many people use a dyno to tune, but as S&S states along with other, if you are going to do a complete tune on EFI with dyno, it should be a step type (i.e. brake dyno) and not the sweep type (i.e inertia such as the typical Dynojet). With a good step dyno run, a good knowledge of what is what and good programming, one can bring the run up in steps, make the adjustment for each and get a much better mapping, verse a quick sweep that does not provide the details one would want for good mapping.
So for me, as I said before, his information is very detailed and entertaining.
I may have missed the main points of his information and may confused people even more, if so I apologize. But on the bigger scheme of things, it is a fourm and he has taken his time to put information that can be helpful. I thank him for such. Bottom line, though is we can read it or not, but I thank him for it.
Also the whole thread is quiet entertaining.
Hey, Knuker!
The loop is forever. 
