HELP - replacement ECM

I have a 2000 4runner 3.4 4X4 federal emissions, that I recently purchased. The previous owner did some welding on the body and I believe they fried the ECM and replaced it with a California emissions ECM. The car runs and drives, does not run right with the incorrect ECM because it is trying to detect sensors that are not present.

I am trying to source a replacement ECM but am struggling. My 4runner does not have a security system with the immobilizer system. It runs and drives with just the metal key. I am finding that the "limited" models had the immobilizer, but not the base and SR5. When i look up the replacement ECM's, everything says that they are compatible for both the SR5 and Limited, which is not the case. The part number that the dealer said is correct for my vehicle is 89666-35140 or interchangeable with 89666-35141-84. Is there any way to know if these ECM's will be programmed for a security system or not? My mechanic has tried a couple different computers and they do not work. I don't know if it is because they are bad computers, or they are for the limited with a security system.

 

Have you considered finding a junkyard Sr5 ECM? I had to once do this for a 2011 Acura MDX similar issues

 

Yes. I am looking at a couple used ones through eBay that accept returns. Where I am struggling is that the more I read about these, the more confusing it gets and I am a little gun shy after the mechanic has tried a couple others already that haven't worked. I am going to pay him for the work that he has already done and figure the rest out on my own. I was just hoping there may be a definitive answer for the one I need.