check engine problem K20 and K24 block

I swapped a K20 into my EG with a K24 block.

But, the check engine is almost always light on. When we run a test with the honda computer, the code is "fuel too lean". What does it mean? I changed my fuel pump but the problem is the same. I have a V2, a DC Race headers and HKS exhaust.

I'm looking now for change the injectors (k24 injectors). Does anyone have a suggestion or a solution for my problem?

Thanks