CARBoy

What have you guys done to satisfy the fuel level signal to the ECU in an LSx? (I have an E40 ECU out of a GTO.) I'm splicing into the OEM signal that goes from the fuel tank float to the Miata dash gauge, which still works fine. That splice then goes through a converter box to adjust the Miata signal (5-120 Ohms) to the E40 requirements (40-240 Ohms), but it's very unstable and is throwing the P0462 and P0463 codes (low and high fuel level circuit voltage) as I adjust the converter box up or down. FYI, it goes to connector C1 Pin 37 in the ECU via a purple wire. And don't say to program it out. I must have the signal for the evap to work correctly, which I need for CARB.

Thanks,
Jon