I just inherited a 97 F250H.D. 5.8l from my grandfather. The slave cylinder was out in the truck when I got it. I replaced it myself. After I got the truck rolling again, I noticed it didn't have a lot of power in town, so I got up on the highway to test it out. It drives fine up to 35mph, after that it seems to lose all power. It is OBD1, I ran the codes, and it threw 12 different ones. I've replaced everything that the codes showed to be bad. Now, it idles better and has more power in low range, and I can get it up to 65mph. It takes almost 4 miles on the highway to get to this speed though. So, I have only been using it to put around town doing things. My check engine light came back on today, and when I ran the codes I got (K.O.E.O) 111, and (K.O.E.R) only threw a 4. I wiped the memory, and drove it until the light came back on, after about 5 minutes of driving, and it says the same thing. I can not figure out what is wrong with the truck, and I would like to get it back up and running in memory of my grandpa. So, any help would be greatly appreciated. I would like to do all of the work myself, so if anyone has any ideas they would be greatly appreciated. Thank You.