Error codes after ECU install

[tee2]

Hello Everyone,
This post, is in a way, a continuation from a previous thread that I had, dealing with issues that I was experiencing after purchasing a used 2001 Pathfinder SE unable-to-diagnose-2001-le-dangerous-as ... 16280.html. I have since replaced my ECU, and now I am getting the error codes, P0105, and P0420. I had the MAF sensor cleaned, with hopes, of clearing the P0105 code. Unfortunately, after the mechanic took off the MAF sensor, and gave it a good cleaning, the code came up a few miles down the road. I have had this whining/pop/grinding/robot being stretched by his legs sound, coming from the car, ever since the day after I purchased it. The sound occurs, after I complete the following steps. Start her up>reverse>drive>sound occurs OR Start her up>put her in drive>sound occurs. It never happens when accelerating from a stop, or driving (at any speed). It doesn't even happen, after the Pathfinder, has been idling in P, and then put into D. I mentioned this in my other, thread, but I have taken it to several transmission mechanics, and they have all told me that my transmission is in great shape. Does anyone believe that this noise, could be related to the P0420/Catalytic converter code? This code wasn't present while the old Ecu was installed, but maybe the old ECU was so badly damaged that it wasn't producing all the errors. This noise level varies. Sometimes, it is extremely noticeable, and at times, it is quieter. Either way, I would say that it occurs a good 95% of the time. Since purchasing this vehicle less than 2 months ago, I have:
Things I have tried:
>Had the dealership run a used car inspection, including engine, and transmission test. No errors. Prior to purchase, the dealership even checked the components related to the smog, and I was told that I would have no problems passing. The car was actually smogged a month before I bought it.
>Had it inspected by a transmission specialty shop. No errors.
>Had a private mechanic test the engine, ABS, clean the throttle body, and replace the air filter.
>Had my ABS system checked
>Cleaned the MAF
>Replaced the ECU (and had both keys reprogrammed)
>Had the throttle body claned
>Replaced the IACV (Before the ECU was replaced)
#######The ECU that was recently installed, is a used model, that I purchased from a Nissan Parts store.

[04pathse]

P0105 is an error code for the MAPS (manifold absolute pressure sensor) , NOT the MAFS sensor.

see pages 160-165
http://www.nicoclub.com/service-manual? ... er/2001/ec

http://www.ebay.com/itm/Nissan-Altima-S ... Lt&vxp=mtr

[tee2]

Yes, pardon me. That is what was meant to be typed. Just had MAF on my mind. Thank you, for pointing that out.

[tee2]

Do you believe that these codes could be behind the noise that I described?