Rough start up

Hello, if you can read that code again, it will be a huge help and give us some direction in diagnosing the issue. My first thought because this happens when you're filling the gas tank is that the charcoal canister may be filled with gas and the canister purge valve is sucking gas straight into the intake instead of gas fumes like it's supposed to. So it sounds like the engine is running rich at start up and that's why you have to push the pedal allowing more air into the intake, compensating for the extra fuel being introduced into the engine. Try to get the code for us, it will help very much. You can also take a spark plug out and see if it is either soaked in gas or has black carbon build up on it. This would indicate a rich running engine. Number 10 on in the picture is the evap charcoal canister.

The codes I got are: P0455 and P0420. What you're saying makes complete sense to me, I just don't know all of the correct technical terms.

The p0455 is a large EVAP leak code and the p0420 is Catalyst System Efficiency Below Threshold bank 1. So the catalytic converter needs to be tested. This code can be caused by a rich running engine or the catalytic converter is actually not functioning correctly anymore. But a rich running condition is what usually causes the catalytic converter to melt down and fail. So you may have a canister purge valve that's sticking open letting too much fuel into the intake causing these conditions and the codes. EVAP leaks can be hard to find sometimes. It looks like the canister purge valve is right next to the battery, if you can, try first clamping the purge valve hose off, and try unplugging it's electrical connector and see if either way helps the problem at all. The purge valve has a round filter on top, inspect that as well. Let us know what happens. You can identify the purge valve by the wiring colors at the valve.

https://www.2carpros.com/articles/evap-system-code-repair

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

I did locate the purge valve, unplugging the connector made no difference. Just this past month it has started to randomly gain rpm without touching the pedal, when I remove the vac line going into the throttle it stops. Would this mean the valve is no good?

Where does that vacuum line go to? And you will need to block off the purge valve if it's stuck open, regardless if you unplug the electrical connector or not, the purge valve can be stuck open. So it needs to be pinched off to stop the gas fumes and air from coming through.