No, the efm does not have the slight vacuum on the ashpan area nor does it have a forced exhaust. The inlet for the combustion air for an EFM is around the fan shaft near where the motor mounts to the stoker unit.. So the 'intake vacuum' is from the room.. This combustion air MAY for a second or two reduce the standard EFM's flue draft when the stoker first starts,, but I doubt if it drops it by more than a fraction of the standard .04-,05"wc. Once the added heat gets into the flue and chimney, the draft will be higher if anything.. then the barometric damper will 'work' to control the draft .
With the AA boilers,, the fan is integral with the boiler, so the combustion air is pulled out of the boiler base, from under the ashpan doors.. there is about a 1" gap under the doors.. this air is pulled through the coal bed, raising the coal fire temperatures, the hot combustion gasses are then forced through the heat exchanger and fly ash separator then up and out the flue.. My draft gauge/Manometer shows about .02-.03"wc when the boiler is not running, the draft drops to about .01" when the fans starts, the returns quickly to .03-.04" the forced flow and heat up the chimney quickly makes for more draft.. I only see pressure in the flue during the first few seconds of the fan starting..