"the "hump" I'm talking about is where you would find the small hubcap with the Volvo logo on it. When they removed the turbo rims and put the black steel wheels on, the two front ones have a pronounced "hump" and the two rear ones don't."

I can't explain why it's like that, but I know that it is supposed to be that way. After driving a while, touch the center part that sticks out and it should be warm. If it's too hot to touch than it's a sign that the wheel bearings need attention.

I noticed that someone mentioned to check the torque of each lugnut by hand. I would recommend that you ask your dealer to torque the wheels to alloy specs even if they are steel wheels. I had a problem with my (former) repair shop that I thought had over-tightened the lugnuts on my steel wheels because when I tried to remove them the following weekend, I ended up with several stripped lugnuts, and one mangled wheel stud. I went back and bought all new lugnuts and had them tightened to 60ft/lbs (alloy spec) instead of 86ft/lbs (steel spec). Now I can actually remove them myself by hand if I need to.

Are the black lugnuts that you have the kind that don't cover the end of the stud, or are they the acorn style like these, except in black?:

If the ones you have now don't look like these, then they probably switched the lugnuts. If they look like those chrome ones, except they're black, then they could have been switched, or painted for some odd reason. Either way, I would go back and exchange the black ones for chrome ones.

Good luck.