Mass Air Flow Error Code - Often Won't Start and Won't go over 2000 RPM

Right now my car will not start, it just sounds like its out of gas, it trys to turn over but doesn't. When it does manage to start; I smell fumes in the car, it takes a long time to pick up speed, it will not go over 2,000 RPM, when I press on the gas it barely accelerates, and just kind of shakes and sounds like a plastic bag under my car. Before this started happening, my car sat not working for 6 months, I had a mechanic get it started and I was told that my gaskets were flooded, he mickey mouse fixed it (it worked, but with less horsepower and a very loud sound!) So I took it to a muffler shop (by recommendation) and I believe all they did was lift it up, noticed a gasket missing, charged me for a gasket ($20), put it on, and the sound was gone and my car was working like new again (but still had a Engine light, with a code saying Mass Air Flow). Well after about 2 weeks of driving fine, that's when my current problem started. I looked at the MAF sensor, it looks brand new, and the plastic bag sound leads me to believe there is a leak somewhere. At first it wouldn't go over 3000 RPM, then it just got worse and worse. And now it won't even start. A few times when it DID start, it worked perfectly for a whole 2 minutes of driving, then right back to the problem. Any ideas of what my problem is?