had the SES light come on last week, scanned it, got some codes

-EVAP MALFUNCTION. and -LARGE LEAK, LOW SYSTEM VACUUM.
possible causes?: (gas door open, unplugged charcoal canister, broken purge solenoid)

-P0420:Catalyst Efficiency Below Threshold. or -P0431:Warm Up Catalyst Below Threshold. it's either one i forgot which hha
possible causes: (bad o2's or cats) ihad a "running rich" code for months untill i got a re-tune, so maybe I slightly messed-up/melted the cats.. idk how possible that is, maybe it needs to be lean not rich to do that

-RANDOM/MULTIPLE CYLINDER MISFIRE
causes?:(i would say the likely cause is from the problem with the cats or o2's or maybe a header leak) I don't think it's a plug or a wire b/c it's random/multiple cylinders not the same one over and over) the misfire must be slight b/c i don't think it drives different or hesitates


When i got the light it said "tighten gas cap", the cap was tight so idon't think it's the problem. Im guessing it's a loose hose. soo.. MY QUESTION IS SHOULD I JUST DITCH ALL THAT EVAP STUFF?



& my rear O2's are off and have been off
also i think it was the STFT's, but lowest it was reading was (5% - 7%) at idle completely warmed up after sitting for a while ...if somebody knows somthin bout that tell me.