My '04 Mazda 3 has started showing engine light and code says EVAP. Have spent $600.00 replacing first gas cap and then vent pipe with no improvement. Car runs fine, no signs of problems at all. Prior to engine light, couple of weeks before, I began having trouble getting gas in, had to drip feed it or the nozzle would shut off - 10 minis. to pump 1/4 tank. Sure sounded like a venting problem but so far just $$$$$$$$ with no fix. Any thoughts?