Help needed down stream o2 simulator

[nik759]

So I had problems with emissions I got a new cat and a new upstream o2 sensor didnt fix it it was a p0420 code so I did some of the things that are recemended didnt fix it so I bought an downstream o2 sensor simulator and im trying to tune in the voltage I put it to 1.00v came back to rich so I put it to.. 2 v came back to lean so I set it to. 36v and didnt have Time to drive it more so iam trying to find the sweet spot wondering if anyone has experience with the simulators trying to keep the check engine light off to pass its a first gen 04 2.7l 4wd tacoma