When i start driving in first and while in second it starts kinda like slightly rocking forwards and backwards, is that normal in my scooby? Also, i was driving tonight and i heard a weird noise that sounded like it was coming from my exhaust so i pulled into a parking lot and parked and revved my engine to listen. It sounded like when i revved it was backfiring(i think thats what is called) when it came back down into the lower rpms. It was a putt putt sound. I have a 02 wrx and it is like 5 degrees here also btw. Any help would be great, thanks.
EDIT: Oh ya, maybe this might be a little important too. I put 87 octane in my tank the fill before the last cause i was being cheap and i know it was a really stupid move.