Problem with car mechanics these days: do much is computerized diagnostics and modular replacement they never (have to) learn to understand cars. Grumble, grumble, grumble. After over $300 of diagnosis failing to identify the problem the best they can suggest is replacing the fuel tank fuel pump and see if they can no longer reproduce the problem. This is possibly a result of driving a high performance car that was only manufactured in small numbers, and imported in far smaller numbers yet. The price of the joy of driving.