1997 Mustang Gt How To Flash Ecu

[kyle ransom]

Hi my name is kyle im new to this site but i have a 1997 mustang gt 4.6l 5 speed and when i bought the car it had a 5 speed tranny in it but the guy i got it from said he put the 5 speed in it. It was automatic and theres a "O/D off" light flashing on the dash and the check engine light is on well i got it check at advance and they said the reason the check engine light is on is because the ecu is still looking for the shift solenoids but they are not there because it is a 5 speed now. Also if i drive the the car it start acting up like gets sluggish rpms will drop the O/D light will go off and the car will run fine for about 5-10 seconds and the O/D light will come back on and it starts acting up again. I'm thinking i can ether flash the computer that's in it or buy a manual ECU. let me know what you think.