Help diagnosing p0420 and throttle/rpm lag

[aPsychedGoat]

I drove 5 hours to an event and hit 160k miles on the way. At the last 10 mins my CEL and traction control lights came on; from what I've read, cruise would have also came on but I don't have it. After the event I got a code reader and it popped the p0420.

I cleared the code and then tried starting the car. It wouldn't stay running unless throttle was applied and I shifted into gear. I've noticed this only happens when the engine is hot. I have also noticed a sort of rpm lag when I apply throttle while coasting. If I'm coasting at below highway speeds, the rpm will drop by 100-300 before rising when I apply throttle.

I've since driven back home and replaced my spark plugs, ignition coils, o2 sensors, and cleaned my throttle body. The rpm lag still persists, and isn't something I've really seen brought up when reading about solving the code. Any insight is greatly appreciated. Kinda figuring I need to replace my cat

 

[Tooj]

If the code is persisting, good chance it will be a cat, you can always try an oxygen sensor spacer, most exhaust shops sell them and they are cheap, if putting that in stops the issue that can confirm the cat is the issue, ive seen spacers completely rectify the issue, but you are just masking a greater problem in the end

 

[aPsychedGoat]

If the code is persisting, good chance it will be a cat, you can always try an oxygen sensor spacer, most exhaust shops sell them and they are cheap, if putting that in stops the issue that can confirm the cat is the issue, ive seen spacers completely rectify the issue, but you are just masking a greater problem in the end

The code has not come back since I deleted it

 

[SimpleMan42793]

Replaced sensors on my 08 Forester, had same rpm issue because I disconnected battery while doing the work. I'd suggest disconnecting the battery (negative terminal), reconnect and then reset your system. It takes a bit but it's a sequence of starting the car and letting it idle, then shutting it off and restarting and idle again. This will remap the TPS (throttle position sensor). Your owners manual should have the sequence in it; if not check YouTube.

 

[aPsychedGoat]

I'll check this out. However, I'm pretty sure it began before I removed the battery connection. Thanks