[MidnightFumes]

My 2014 FRS has been in what I believe is "Limp Mode?" for a few weeks now. It runs and drives well except for a shudder when coming to a stop and a decrease in power. I've also noticed that all lights go away and the car drives like new when I start the car and my gas tank is on or under 1/4 tank. The lights come back on once I fill my tank up and drive off.

CEL Codes:
P0016 Crankshaft Position - Camshaft Position Correlation - Bank 1 Sensor A
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0016 Crankshaft Position - Camshaft Position Correlation - Bank 1 Sensor A

Extra Info:
I've talked to quite a few shops and was told they'd need it for a few days (I daily drive it and need it for work so I sadly can't do that), or they had no idea what it could possibly be and that I'd need to take it to a dealership. I called and went to the nearest dealership (Toyota) and they blew me off pretty hard by telling me they couldn't work on a Scion because the engines were completely different than the Toyota ones... I thought they were practically the same but oh well.

Luckily got in contact with someone to come take a look at it and he said the Exhaust / Catalytic Convertor was clogged. Not exactly sure what that meant considering I'm illiterate when it comes to cars but I was wondering if anyone else had this issue? and what they did to fix it? I'm willing to work on it myself if I can get an idea of what's going on. Thank you.