LOUD Engine sound on start, while driving / low acceleration

It's a 2007 Prius. Got it used a couple years ago, been driving fine for a while. I drove it a few days ago, no issues at all.

Today, I went to go to the store and immediately the car started making this LOUD rumble. Like an old hot rod at a car show.

The low gas light was on (I think it came on right when I got home a few days ago, so it shouldn't have been too low). I walked to the gas station, got a gas can, gallon of gas, and some oil, just to be safe. Put the gallon in, added more oil (although the levels looked fine I think?) and tried starting and stopping a few times. No change.

Even drove it around the block - extremely low accelleration, and the loud rumble is directly tied to accelleration. When I hit the accelerator, it would get louder. When I slowed down to idle at a stop light, it would almost dissappear, and then come back when I drove again. Entire drive around the block was incredibly slow.

on that drive, I got an error code p0037. which is: Heated Oxygen Sensor Heater Control Circuit Low, Bank 1 Sensor 2.

I just wanted to check here first to see if I'm missing anything stupid, before spending all of my savings at the mechanic. Thanks in advance.

 

You're right I think. I jacked up the car and it appears, from what I can tell, that it has been sawed out from under the car.

 

Yep. Just moved to LA and am quickly discovering how great it is..

Yesterday I was incredibly frustrated and angry. Today I'm doing better and need to figure out how to move forward. Catalytic converters appear to be super expensive ($2000ish) and this car I got used and has a long history of problems (although it has been running for around a year now. I still don't trust it)

Trying to figure out if I get it fixed at a mechanic, or go for a new (used) car. I'm worried if I get this fixed, the thief is just going to come right back next week and steal it again. Is there a cheap way to prevent this? Or should I start car hunting?