Hmm wouldn't let that mechanic near my car! Fuel pump relay is switched on/off by the ecu (pin 28), it doesn't send a variable voltage to it, it simply earths the relay.

Is your tps connected? Or as mentioned above the ect sensor (blue) might need replacing or plug to it maybe faulty, if the ecu doesn't detect ect signal it will overfuel as it thinks it's cold so pumps extra fuel in.