1997 F250 7.5 runs rough and poor MPG
 

I have recently purchased a 1997 Ford truck and it only is getting about 4 mpg just driving it with no load, it runs rough and wants to surge when i come to a stop, then it will die. it has even compression and a new tuneup. it has a code 0171 and 0172 can anyonr help me with this problem?