hi sages- one of my car rules is to do anticipatory maintenance and learn about mysterious devices on the car far in advance of one of these devices crapping out on tobacco road cornering me into being soaked by a shyster mechanic or dealership.this rule coupled with only buying a tried and true rwd stickshift design like a 240 or dodge slant six has saved me many thousands. i know i have a bad attitude. one such study for me is the air mass meter. what i have surmised is that it is a mpg improvement and smooth running device. my 92 240 wagon 5 speed consistently pumps 25mpg around town and runs smoothly. so i think the amm is running swell. i understand when it craps out it sends a message to the computer which tells the injectors to enrich the fuel mixture which sends the mpg down the toilet. given its position on the intake air path, it appears to measure the air velocity. how exactly does this device read the air characteristics? since it is expensive as hell which brand at the auto parts store is best. would you suggest rock auto which has name brand parts? also it appears amms crap out due to the air intake thermostat which can send too hot air through the amm killing it. living in fla dont have to be concerned about cold weather running. uncle moe says to block closed the flapper on the stat which keeps the hot air duct closed to the intake. what think you sages? thanks tons oldduke