Few problems with some OBD II Codes 1996 Ford F150 Straight Six
 

Ok i fixed some problems on my 1996 Ford F-150 Inline 6. I had a major misfire for about 3 months but had to deal with it. I fixed it then had to put a new downstream o2 sensor in because it was throwing codes and we determined it was it was bad. The check engine light stayed off for about 100 miles then came back on earlier today. I went to get it checked now I am getting P0174 and P0420. I know what they mean but I need to know what could cause these codes. I need to figure out possible fixes. Im thinking the Cat might be bad from me letting it misfire for so long but why would it be saying sytem to lean bank 2 also. SO maybe the system being to lean might be causing the Catalytic converter to not be working properly. Ideas please.

P0174 -- System Too lean (Bank 2)

P0420 -- Catalyst System Efficiency Below Threshold (Bank 1)


Here is a site I use for OBII codes

http://www.obd-codes.com/trouble_codes/

I know what they mean but what would cause these codes most likely. In other words should I invest in a new cat or what. And how do I stop the to lean. SHould I adjust the distributor. These are the questions I am asking. I need help its anoying the fire out of me.