2004 Ford F250 - CEL

My check engine light came on. Said rich on one side lean the other. Checked catalytic converter, no. Checked the oxygen sensor both, no. Checked vac leak no, Checked manifold leak,no. Checked injectors replace nb 8 still did not clear check engine light. what else can it be?

The actual codes would do us a world more good than just a description. A year, engine type and size, transmission type, and how many miles would be an amazing help as well.

How, exactly did you check the cat? How did you check the injectors?
What is an “nb 8” ? Number 8?

Do not know the engine, had a lean bank error code, ended up being bad o rings in the plenum. $500 or so to fix, other mechanic stumped. It may be time to take it to a Ford dealer.