Sorry it took a while to get back to this but I’ve finally done some tests, or at least tried to. First to answer your question. I did one oil change when I first purchased the car at 120,138 miles. I did another oil change at 122,986 miles when I changed spark plugs and valve cover gaskets. I don’t remember any significant oil loss, at least not like what I’m having now. If I lost about 1.25qts over the past 524 miles, that means I would’ve lost almost 7qts of oil, which obviously would be noticeable 
I put 5W-30 because that’s what’s on the oil cap and booklet, and I used full synthetic Royal Purple because I thought I might as well use the good stuff on this top-end rebuild (not trying to start an oil debate here, just what I did).
I changed the PCV when the engine was out of the car.
Now onto the test. Please understand that I am no mechanic and it’s the first time I’ve tried this. So far, I have not done a leak down test nor do I know the difference between wet or dry compression tests (I only noticed the comments about these tests today).
Compression test:
I let the engine idle for over 10 minutes before starting the test.
I removed the air filter system all the way up to the throttle body.
I purchased a wired trigger starter and connected it to the battery terminal on the starter and to the starter signal prong. My understanding is that this allows me to perform this test without the key in the ignition and without having to disconnect fuel pumps and such.
I removed all the spark plugs, threaded the dial into spark plug 1 and loosely slid the spark plug boots back into the other holes (without spark plugs, mostly to prevent stuff from falling in).
I inserted a plastic piece into the throttle body to hold it open while I held the starter trigger.
I let the starter crank the engine 3 to 5 times, took the reading and proceeded to continue the test in the same order as piston firing.
Piston 1: 192psi
Piston 2: 191psi
Piston 3: 187psi
Piston 4: 191psi
This seems abnormally high! My understanding is that it’s supposed to be between 140 and 170psi but am learning that it’s dependent on engines, maybe? I haven’t looked at possible causes for these numbers yet. Maybe my gauge is off too.
Though all high, all piston compression values seem to be close to one another.
By the time I reinserted the spark plugs (with anti seize), the spark plug sockets was still quite hot (engine was warm throughout the test).
The spark plugs, which are as old as the head gaskets (about 2,000 miles), seem to wear slightly unevenly. I don’t know if this is abnormal wear for so little miles.
The piece of plastic I used to prop the throttle body open came out covered in black gunk.
I did not clean the throttle body when I worked on the engine. The back of the throttle body itself seemed pretty dirty.
Head gasket leak test
I purchased a block tester kit and followed the instructions. Notably, they recommend removing coolant to make sure the level is 2 to 3 inches below the neck, I did so.
I fired the engine up, which was still warm from the compression test, and performed the block test.
I did not notice any color change in the liquid as I was pumping air through it. However, the coolant level seemed to rise and I stopped the test before coolant started being pulled into the tester.
I repeated the test by removing more coolant and replacing the used testing liquid.
Same thing happened, though it felt like even more so, as I only noticed the coolant rising through the test tube (only a little), which of course changed colors slightly.
Results:
The liquid didn’t change color, however, don’t know if this is a conclusive test because of the rising coolant. I’m not sure what to conclude from this.
Other notes
I noticed that the intake manifold gaskets, especially on the passenger side, are damp with something resembling oil and so are the lower 2 inches of the intake manifold.
I sent a descriptive email to the shop that overhauled the heads. I’ll follow up with a call tomorrow.
I am also getting ready to leave for almost a month. I doubt I’ll be able to do any other test with this car until I return. I believe I still need to do a leak down test. Maybe these initial results can help pinpoint what’s wrong. I’ll look up reasons for high compression numbers too.
