Truck started doing this

Starts - dies
Starts - dies
Starts - can't shut off with key

Replaced Fuel Shutoff Solenoid, replaced starter, replaced starter/fuel relay, replaced air filter, now have no power and will not run. Have wired Fuel Shutoff Solenoid open so it will continue to run (have to shutoff manually, key won't shutoff), 2000 rpm's is the best it will do, uphill or downhill, in 1st gear or 5th. Somebody give me some pointers. Never had problems with this engine before.