I have a 2000 ford focus i changed my Mass Air Flow Sensor twice already?

There is no fault code for a failed MAF. If anything the engine will read as being too lean or too rich and the MAF is just one possible cause of that condition. One actually has to watch what the MAF is doing and know what it means to determine if it is functioning properly. Clearly if you have replaced it twice your problem is not the MAF.

Just think backwards, your engine is failing because the mass airflow sensor is failing. At some point your realized this and decided to correct the problem, now you know that something is causing the MAF sensor to fail, you need ot fix it. The MAF sensor is only exposed to incoming air, so something is coming into your intake and fouling it up, its probably a leak somewhere in the air-box, or on the hose connections prior to the maf sensor, or perhaps something is getting in there that its not supposed to, such as cleaner for a k/n filter as somebody suggested, maybe theres oil/coolant dripping on it somehow, whatever the cause, something is causing it to fail, and you need to find it. I once saw in a store a special cleaner just for cleaning the wire inside a MAF sensor, maybe it wil revive your old one?, idk, but it was only like 5 bucks so its worth shot since MAF sensors are kinda pricey.

check your air box for cracks and make it is sealed correctly so dirt doesnt get on mass air flow sensor. also if you have a k&n style filter and over oil it it will ruin sensors.

Does anybody actually test parts before they toss $300 at another part anymore??? I bet your code was P0171 and your money tossing was at the mercy of a simple vacuum leak that has yet to be found. Wow.