Ford f 350 engine control computer situation
 

Good day, I have f350 ford that was used at an airport. The vehicle can only do 25 mph.
I suspected that engine control computer could have been programmed to retard I bought new computer and had it flashed and shipped to me here in the caribbean St Kitts/Nevis.
Engine will not start with new flashed computer
old computer still works
What should I do?
Need some advice , please.
Thank you anyone.
christian Rameshwar