Had the CEL codes pulled today at Autozone and saw some new ones. Any reason to worry?

First Code: P0455 - EVAP large leak detected.

This has been firing since I got the Cherokee back in 2001. Jeep couldn't figure it out and I discovered it was a busted seal on the gas cap. They replaced it and the CEL light went off. No joy the next time if lit up, haven't figured out what the problem is, and neither did any of the mechanics I took it too.



Second Code: P0303 - Cylinder misfire detected-cylinder 3

This started after Jeep put that stupid heat shield on top of the engine. It traps all the heat and cooks injector 3, making it vapor lock. It usually clears up if I let it idle for 60-90 seconds. There is no known fix for this according to Jeep, Autozone, NAPA, or O'Reilly's. I'm thinking pull that shield off, and vent the hood.



Third Code: (Not Seen Before) P0500 - Vehicle speed sensor circuit condition.

The explanations their system offers are worrying- Poor electrical connection or short circuit, failed vehicle speed sensor, and/or drive gear mechanical fault (the scary one). Any ideas where to look first?



Fourth Code: (never Seen Before) P0432 - Catalyst efficiency low-bank 2

There are 3 things that look like cats on this puppy, and nobody seems to know which one this is referring too. This also mentions oil leaking into piston from exhaust valve guides or piston rings, but I never see any smoke.

Suggestions appreciated!

 

first code- have a mechanic hook to an evap smoke tester to the fuel filler neck and clamp off the vent where smoke starts to come out that's your leak

code 2- never heard of this problem so i cant help you there, sorry

thrid code- check the speed sensor on the back of the t case it could just be the connector dirty

code 4-Im assuming your jeep is a 2000 or 2001 the bank 2 convertor is the rear one in the picture

 

Thanks!