New to the forum, need help on issues with santa fe

Hello,
I have a 2007 Santa Fe. I am the second owner, and i bought in 2009. around 2011 I started to have a problem with it not going passed 20mph. it would start up than as soon as i hit the street and accelerate, it wouldn't go any higher than 1500rpms and any faster than 20mph. I looked online and found what i thought was a solution. it said to clean out the air flow censor. which i did, and it seemed to help. I dealt with it not working all of the time for the pass 2 years. just turning it off and on until it worked. Now just this last month it started to do it while i am driving down the road, and this last week i cant get it to work at all. All electrical works, everything works except go faster than 20mph. If anyone has experienced this and has fixed it please help point me in the right direction!