So today on my way to work I saw a check engine light come on. During my lunch break I went to auto zone to get the code checked and the guy told me it was pulling a bad TPS sensor. I went back to work and figured I'd pick one up around the corner from my house when I got off. The 4runner ran completely normal all day at this point. I may have noticed a slight rough idle but nothing major. Anyway, as I was about to leave work I turned the truck on and it sounded like I had flow masters or something installed. It was a loud, low rumbling sound. The noise just came out of no where. Anyone have any clue as to what it might be?