Hi Earl,
Really enjoy your posts, sir. And this one is about one of my favorite topics: Internal Combustion!

I am not going to go into a lot of questions about this, but, in an engine, with dual mags, which mag fires spark plug nearest the exhaust valve?
The twin-spark engines I've seen inside (old Maserati in-line six, modern Lycoming IO-360) have one intake and one exhaust valve, with the two spark plugs equidistant from the valves. With two valves and two sparks, they're ranged around the periphery of the head at ninety-degree intervals: valve-spark-valve-spark. Along that same line of questions, why is it normal for the L and R mags to have a difference in RPM drop?
Depends on how the intake mix swirls into the cylinder while the piston descends, and how close the currently active spark plug is to that swirl. In many engines with two-valve heads, the intake charge flows into the cylinder in a sort of corkscrew path.When using an exhaust temperature gauge for maximum fuel range, how do you arrive at that peak performance?
Lean the mix slowly until you see the highest temperature (most complete combustion)... and then enrich the mix "a skosh" to keep the engine a little cooler.Why is it important to know where your fuel pickups are located in your fuel cells?
So you can know what attitude and/or G-load might cause fuel starvation, I suppose?Who or what organization, sets the fuel grade of different grades of gasoline for aircraft?
Depends on which country you fly within. 