97 civic ex. Why is my check engine light coming on only when I floor it?

I added a intake and full exhaust then the check engine light came on. The code said its the O2sensor. My friend had a ecu that I bought from his 96 civic. I bought a Phearable.net Custom OBD1 28 Pin Eprom Chip Basemap and a OBD2A to OBD1 ECU Jumper Conversion Harness For Honda Civic 1996 1997 1998. We hooked everything up and no check engine light. I coud drive it around all day and no code but as soon as i floor it, the check engine light comes on. When i turn the car off and back on, the light is off and only comes back on when i floor it again. Has anyone else had this happen to them?

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