My Chevy sounds hungry

I recently bought a 1996 Chevrolet Cavalier LS with 88,000 miles on it. I detected a rumbling or gurgling sound coming from the rear of the car on the test drive. I convinced the dealer to knock the cost of a muffler off the sale price, since that appeared to be the obvious problem. After having the exhaust work and some transmission maintenance done and replacing the front brakes and all four tires, the noise remains.

Is the noise present when idling?

No. Only when the car is in motion. It seems to get quieter at higher speeds, but that may just be attributed to additional road noise.

Could you just be hearing the air being trapped in the rear of the passenger compartment?

Rumbling and gurgling to me are two different things. Can you do better?

Does the sound change at all (even if briefly) if you turn a corner?

I would call it more of a rumble, since gurgling implies the presence of liquid. Very little difference in the sound (and slight feel) occurs until the car actually stops moving.

Investigate the upper mounts on the rear shocks.

It could be a rear wheel bearing, an independent mechanic can hopefully provide a full diagnosis and repair options.

I wonder if it may be real gurgling. Maybe the fuel vent system is clogged.