I live in the suburbs of Washington, DC and am working with a Los Angeles-born neighbor to clone the awesome burgers served at those independent char-broiled burger joints, many of which have "Super Burgers" in the name of the establishment. One place (now closed) that I used to frequent on visits out there was called Andy's Super Burgers on the corner of Slauson/Mulberry and Santa Fe Springs in Whittier. Another favorite was Douglas Burger.
While I can obtain foodservice buns and condiments, I have not been able to recreate that char-broiled flavor using a gas grill, charcoal grill, liquid smoke, etc. There is something missing. One possibility is that they are buying flavored burger patties. Another possibility is that they are using a industrial food ingredient called "grill flavor". Of course, it could also be technique. Anyone have any insights into the meat they buy, the temperatures they cook at, etc?