If you try to check for misfires (put the engine under load at low rpms) it seems to act a little funny, but I'm used to the low-end of a V6, so I dunno if it's abnormal...?

what do u mean? describe what ur trying to do(like to check for misfires) and i'll do it tonight, tell u what i find out

the only misfires i have noticed is when plugs went bad at 82k and when O2 went bad. other wise no misfires.

ok...if I start to go up a hill and I am in a higher gear, say 4th at 50 MPH (i dunno if that's a speed that I could do it at, just an example), and I start to ease into the throttle, but not enough to downshift it, it seems to turn into the little engine that couldn't...It just seems like it's kind of jumpy and sometimes it downright stumbles. I know that doing that (accelerating under a load) puts a lot of strain on the engine, hence why it downshifts half the times I try to do it, but i wanna make sure this car is in full working order before I install the header, caulked motor mount, and Mobil 1 ATF.

I agree with Oldsman. Check your plugs. Then if that doesn't help replace your front o2 sensor(the one in the exhaust manifold). I just replaced my front o2 and it's like a whole new engine. I replaced mine a little late, 120,000. You should probably change it around 60-80,000 or when it fails.