The ECU will occasionally want to trigger a fuel tank purge valve. The purpose of this is to vent fuel vapour from the charcoal canister into the inlet manifold. In general, this is a good thing. However my UK model MGB never came with a charcoal canister. We vent our fuel tank to the atmosphere.
Perhaps at some point, I’ll install a closed loop vapour emissions system, but for now, I want to bypass this function. Once again, the ECU just wants to see some evidence that a relay has fired, so the same trick will work here as for the SAI. Bridge the purge valve connector with a 100-200 Ohm resistor.