Was the car mapped on texaco? Its not a very good fuel. If it was mapped for say shell vpower the ecu will have detected knock and pulled timing and if bad boost as well. Try a decent fuel. Subaru engines like shell vpower, tesco 99 and if there is no other choice esso 97. Subaru engines really dont like bp fuel. I believe texaco get there fuel from bp for the super, well its very similar power wise.