P0420 and P0325 on 2002 civic sir
 

0325- knock sensor circuit malfunction
0420- the dreaded cat converter bank 1 malfunction

more worried about the 2nd one. How bad is it? Whats the damage I'm looking at? And if it's a bad cat can I use an aftermarket one as replacement to pass aircare? Can't afford the 1300+ for an OEM one :(

It depends on how much you have modified your drivetrain. Aftermarket cat usually have less precious metal and surface area.. so your readings will be higher if your tune is on the rich side etc.

update: got a universal cat. passed A/C. 325 cleared by itself.

its good to hear that you got universal cat. you have found easily? how it cleared by itself?