while pursuing the P0455 code on my '97 E320 was to 1) put a good squirt of WD40 into the side of the purge valve which has the line running to the rear of the car and 2) removing the rubber gasket from under the fuel filler cap and flipping it over. So far code has not come back. Seems more likely that the WD40 is the reason but the flashing fuel guage light is supposed to indicate a leaky or missing fuel filler cap. I'm not 100% convinced that the problem is cured but I have over 500 miles added since these "fixes" and no codes or flashing fuel guage lights. FWIW.