The engine kept choking on the back exhaust because the cats were not working. After paying $600 to a Subaru dealership for a engine check and spark plug replacement the issue was still present. They told me it was the catalytic converters. I then paid a mechanic it clean the cats out. That didn't fix the issue. It turns out you cannot clean a bad catalytic converter. Once one goes, it must be replaced. Subaru pipes are fitted in such a way that universal cats do not work so I had to get exact fit cats, which cost me another $1250 (O2 sensor was stuck so it had to be replaced as well).

The theory as to why the cats went out is two points, 1. the upper cat is too close to the engine which results in over heating. 2. poor combustion of gas resulting in buildup and contamination of the cats.

The ignition coil just went out today. It is possible the ignition coil has been going out for some time, which is how so much fuel made it through the system to contaminate the cats.