Ash Shah

My daughter has a 1999 Volskswagen Beetle which she brought from FL to NJ.
The check engine light is on all the time. Had it reset but came on again yesterday. The diagnostic codes are as follows:
PO172 - System to rich bank1
P0455 - Ecaporative emission control sysytem leak detected (gross Leak)
P0302 - Misfire cylinder 2

The car has some mods - intake has been changed from the original flow to one that is mounted directly. It looks like a large filter connected to the hose. The exhaust has been modified from the back of the catalic converter to the tail muffler - sports with a loud noise. There is no inspection on cars in FL. Recently the car went through a basic service.
The codes above were cleared but after driving for a while the CE light is on again and the engine started to run rough. Almost slow to pickup speed. Let it cool down overnight and the engine seems smooth again but CE light still on.

Local mechanic indicates expensive fix and no guarantee if it will resolev the problem. Any suggested fixes. Is it worth fixing?