2000 Avalon Check Engine Light

[yota76249]

Hi I usually just read the forums here looking for advise and don't ask questions but i am kind of at a loss because i need to get my wife's car inspected but it wont pass with the check engine light on. I have searched and read but really am not sure of my next step since I have several codes.
The first time i read the codes i had P0171, P0330, P0420
I cleared the codes and took it out and drove it. It didn't take long at at for the light to come back on. Maybe 10 miles. i ran the codes again and the P0330 was back. knock sensor bank 2. I cleared it again and drove it some more with the same result same code. I had to do a few things while i was out do I drove it maybe 30 miles and ran the codes again to have the P0330 and the P0420 code but the P0171 which I figure is an O2 sensor acting up.
what I have been reading on here. The knock sensor is under the intake. Is there a way of checking this out without pulling the intake first? Is this the first code I need to fix first? Also P0330 came back pretty fast could these 2 codes be related? I had read the codes about a month ago and this was the only code I had then.
Im not sure if I have given enough information or not but any information I could get i sure would appreciate.
Not sure if it helps but the car has 195,000 miles on it
once again Thanks so much for your help in advance and for all the other ways yall have helped in the past.

[csaxon]

Start by cleaning the MAF and look for cracks or tears in the air intake hoses. Sometimes the 171 (lean) can cause engine ping which triggers the knock sensor. http://www.toyotanation.com/forum/t96508.html Read whole thread.

[yota76249]

Thanks, I have checked that pretty good. I have also pulled the MAF sensor out and cleaned it so many times I have wore out the screws but I will double check that again. If I do replace the knock sensor. Do I need to use OEM sensor? I need to get this fixed pretty quick so I can get it inspected.
All advise appreciated and thanks to all.