Last Christmas my explorer died on me and it was becasue one of my after market battery cable had come loose on the battery. I fixed it and that is when it started running like it was chugging for air. Nothing super bad just a little bit. I replaced the battery cables, the spark plugs, the air filter and it was getting worse. now I would push the gas and sometime is would go some times it wouldnt almost like I blew a header or 2. I took it to a shop to get it looked at and after $200 they told me it was the Mass Flow Air Sensor. I told them I would replace that my self to save myself another $100+ more. The new MFAS didnt fix anything how ever with it unpluged it runs great except now im only getting about 10-11mpg. Any one have any ideas on what could be causing this?