The computer monitors its systems, if there was too much fuel or too little then you would get a CEL.
MAF sensor tells computer how much air is coming in so it can calculate the amount of fuel to add, but it can't tell if there is a restriction pre-MAF that is limiting air flow.
Same with O2s, if there is the correct amount of oxygen in the exhaust then as far as computer is concerned all is well.
If exhaust has limited flow above 1,500-2,000 RPM then back pressure builds up which causes less new air/fuel mix to come in on intake stroke(and less air pulled in at MAF sensor), so less power but the the O2 still shows "good" burn, because the air/fuel that did make it in was correct 14.7:1 ratio, so no CEL
Engines are air pumps so a vacuum gauge can tell you alot about it's condition.
You also loose the negative pressure in exhaust system at mid-RPM range even with a small restriction on exhaust.
Rangers have a tuned exhaust system, at the mid-RPM range the tune causes a lower pressure at exhaust valve ports, this pulls exhaust out of the cylinders when exhaust valves open, so the piston and crank loose less energy pushing it out.
This is called a Scavenging exhaust system.
Most after market headers are tuned for low RPM range, so create the lower pressure at the exhaust valve ports sooner in the RPM range giving engine more low end power, you do lose mid-range with this.
And there are Racing headers that create this lower pressure at high RPM range.
Factory tuned exhausts are where the Myth of engines needing back pressure comes from.
People removed the factory exhaust manifolds and installed "free-flow" manifolds, larger pipes, then go for a test drive.
"Hey, WTF, I lost power!!", "This engine must need back pressure"
The result was correct, you would lose power, but the conclusion of why is not correct.
The smaller factory pipes created the velocity in the exhaust manifold system that creates the lower pressure in a specific RPM range, when they put on larger pipes at the heads they lost that velocity and so lost the Scavenged power it provided.
No 4-stroke engine runs better with back pressure
Any part with a large enough mass/weight can be damaged in a sudden stop, torque converter full of fluid is pretty heavy, but I think you would notice it slipping, if RPMs climbed up but speed was slow to respond, like a clutch slipping in a manual trans.
Now the torque converter is against the crank which also has some weight to it, and the crank is held in place by thrust bearings, length wise.
Torque converter is not 'attached' to the trans, it slides in and out on the input shaft.
A sudden stop while engine is running could damage thrust bearings, big maybe on that though, only way to tell is to check end play on the crank.
I don't think it could bend the flexplate because torque converter is pressed against crank in the center