mgranzow & Brian94Cobra-
thank you both for the prompt replies.
The best my brother and I could figure out was that each setting on the meter represented and "read" the same thing, but that the range was different. What we didn't know was where to put the decimal, and the whole "20-200-2000" thing threw us off. I figured that the "k" represented 1000, but I didn't know if 20k meant to multiply by 20 thousand, etc., and the fact that the values shown on the meter (5, 5.5, 5.56) were essentially the same threw a wrench into that theory as well.
But, Brian94Cobra, what you are telling me is that "20k" and "200k," etc. are merely representations of the particular range of resistance that particular setting on the multimeter displays as output, i.e. the 20k setting measures up to 20,000 ohms, while the 200k setting measures up to 200,000 ohms, etc.
What is actually displayed on the LED is essentially the same for all intents and purposes for this particular application; it's merely a matter of how it is "represented" or displayed. Therefore, if my #5 plug wire reads "5.56" on the 20k setting, that means that it is actually 5,560 ohms for 17", or 3925 ohms/foot. The same wire reads "5.5" on the 200k setting, equating to 3.88 ohms/foot. So, the moral of the story is to read the ohmage with the lowest setting possible to get the truest results..?
Interesting. Very interesting. It makes perfect sense! Now, if the multimeter was just a bit more intuitive a moron like me might be able to figure it out. Or maybe not.
Now, assuming that my horrible math is correct, 4000 ohms/foot isn't too terrible for 8 year-old-somewhat-neglected plug wires. Now when I switch over to MSDs or ACCEL I'll totally be able to shut down my brother's '99 35th anniversary GT
(side note: for a 4.6, that thing make a hell of a lot of low-end power)