HELP rough low idle code 0

Let me start by saying, I have a fully built b16a that went down due to a transmission about 6 months ago, I just had enough time to put the new one in, and to find out in a move I had misplaced my ecu. so,As you can see by the title, it says “code0”. Would normally say just replace the ECU. Well, i did that! lol I got a socketed p06 with vtec added and such. I rode in the car with the guy before I bought it. It ran beautifully no CELS. I figured this would take care of my code 0 woes. It didnt. I have a rough idle, almost like its misfiring, it is running really rich also. However, you rev the baby up to 3000 and damn she is beautiful. No misfire or rough feeling, but once it hits below 3000 she wants to die. By low idle i mean like 100 rpms.
List of what has been checked
-Grounds tested for continuity
-Fuel injectors have proper resistance
-The o2 sensor needs replaced (shouldnt cause an issue until its 600 degrees)
-map sensor checked great

I have attempted pulling codes over and over, I’m not a newbie, but I am stumped.

Any help I will love you forever!!!

So you lost your ecu and bought a new one? Is your check engine light on? At idle and when you come to a stop, you’re at 100 rpms?

CEL is on, when pulled its a code 0 (Constant cel on, doesnt flasg codes remains solid) this usually indicated a bad ecu. At least 100!!

Its most likely your ECU. Its bad.

I bought a ecu for my Lexus LS400 a while back. Lexus ran fine before that. That ecu was bad. CEL came on, it misfired a lot, car ran rich, bogged and stalled a lot. But just as you described, once I took it over 3k rpm and it was over 20 MPH, the car ran awesome. With the bad ecu, it feels like the car has all kinds of shit wrong with it. I couldn’t even get pull a code from the scanner. Took to many shops and they were clueless and told me to replace engine. Other shops said transmission lol. The dealership said complete engine. I found a good ecu from a wrecked Lexus and when plugged it in, everything was back to normal.

Try replacing ecu with a stock one first. However, hard when only the seller may know if its a good or bad ecu. Best if you knew someone with a good stock one(not a tampered one) and plug it in to see if it corrects your issues before you go spending any real $$$.