no Greg, you just explained yourself incredibly well, you just said in your own words many thoughts/ideas I've had for so long now!
See it's like you have read my thoughts and restated them better than I thought them!!
Probably 'cause my new Alcoa Fedora wuz off, I was smoothin' sum wrinkles in it. Didja know there's this 'lil tag under the brim that says sumthin' 'bout wearin' it outside durin' lightnin' storms? Shoot, ah think I'll look kool wearin' it while I'm flyin' my foil kite
You guyz shure know howta spark my imaginashun...

(groan...)
The contrasts between Karl's and Greg's two stories of their Mazda trucks, is trying to tell us something. Back to basics. Engine needs fuel/spark/compression to run.
Greg has had results each step of his way.
Karl has had huge frustration.
I've had suspicions re: these re-badged Ford's and the engine power/weight ratio.
If a vehicle is underpowered in operation, as a driver you wheeze along w/ your foot in it, right? That's exactly what my Subaru wagon was when I bought it over 10 yrs ago. (Bought it for courier work). It's easier to increase power, AND reduce some parasitic losses, than reduce vehicle gross weight. Analogy: Why does the fat kid shuffle along looking strained walking up the hill, while the athletic trim kid saunters right up the same hill? Power-to-Weight.
Compression: Karl's engine measured quite well there
Spark: Karl has done the coil-pack re-routing trick, and has 2 Torquemaster plugs per cylinder. he's probably AT LEAST adequate there.
Fuel: Well it's getting some right?? Details? I recommend a Ford forum search to see if anyone else has posted about this (potential) issue. Yes, Karl definitely get the pressure at the rail checked. Greg got better operational results w/ his new fuel pump? Even better MPG?
To me Greg's results w/new fuel pump is a huge clue. If this hunch is right, it's a real lesson.
Karl, we've turned over lots of rocks lookin' for the Gremlin in your Mazda. Could this be it? Also- can any other component in the fuel delivery system be a factor? If this is IT, it reminds me of how I became an Ignition fanatic. Stock/parts store plug wires LOOK OK, the engine runs, you can't understand or see any difference, until you measure resistance w/ a digital ohm-meter, then do a tuneup w/ performance/low-resistance ones, and FEEL the difference.
FUEL- if anything causes the Injectors to deliver a sub-par spray pattern, it's like a carburetor that needs a rebuild, it runs, but not at best. It ought to be obvious--we here are striving for Above Average Performance, how else can you get top MPG? You wouldn't expect to get top performance while driving w/ the parking brake partly engaged. That's Obvious, you can see and Operate the park brake manually, you know all about it. But there's no fuel pressure gauge to look at. The pump is back in the dang tank, how ya gonna look at it? And most DIY'ers don't have a fuel pressure test gauge set... (wow Greg the regulator is in the tank too, so it's not man. vac. referenced?) Can this fuel system in these Mazda's be so forgiving as in it'll still run, but have sucky MPG or power?
Again-fuel/spark/compression, well Karl's spark/compression is likely ok, that leaves fuel.
I didn't start getting good even occasional phenomenal MPG's until the Subie's power issues were fixed, and it's relatively light... Better Efficiency is another word for better MPG & Power.
OK I gotta smooth my hat now...
Tracy G