'97 Pathfinder Codes - Anyone know the problem source?

[Iceman2989]

I recently purchased a 1997 Pathfinder, and after checking the check engine light received the following codes. Does anyone know where the main problem may be from looking at this list? I am new to working on cars, but would like to do as much as I can myself before taking it in to the shop. Thank you all for your insights!

P1447 evap purge flow monitor.
P0420 catalyst system below threshhold (bank 1)
P0430 catalyst system below threshold (bank2)
P0325 knock sensor 1 circuit (bank 1)
P0505 idle air control system
P1441 vacuum cut valve bypass valve
P0443 evaporative emission system purge control valve circuit
P0446 evaporative emission system vent contol circuit
P1105 map/baro pressure switch solenoid valve


Its a big list I know, but if there are any of these things that are coming from a certain single problem, I'd like to know the problem area. Please help!