My mother ahs a 2000 Satyrn S Series (SL-1) 1.9 L SOHC and she says that when she drives her car it sounds like an airplane. She says that it's really loud and it sputters. I have the Car MD and it gives me the code PO442 (medium emissions leak) so it can either be the fuel cap, fuel tank pressure sensor, or fuel pressure regulator? I need ur help. We already replaced the cap, so what else can it be?

Sounds like an exhaust leak. Saturns are common to leak at the front of the flex part, just under the engine oil pan.
As far as the code, I replaced a bad vent solenoid on my daughters saturn. This is located behind the left rear wheel. It opens and closes the evap system, and if it fails, could cause this code. You can test it by applying 12 volts and a ground to see if it opens and closes.

If sounds really loud and the sensor is showing that code, check the exhaust. They will put it up on a lift for free to see the problem of a "loud noisy sounds" maybe even find out what is wrong with it. Just a shot for a little free help. Might be exhaust since it is so loud. Could be exhaust manifold or something stuck under the car.