360 LA installing Promaxx Aluminum heads

That’s not terrible placement. Within 18” of the collector is ideal and I think you’re there. But you are only reading one bank and have a dual plane intake so cylinder to cylinder distribution may be at fault here. Basically what I’m getting at is don’t trust the sensor for gospel. Give the engine what it wants and rely more heavily on plug reading. Speaking of that can we see a plug?
I'll pull a few tomorrow.