I currently have a 95 F-Superduty with a 7.3 diesel and a manual transmission. the problem I am haveing is that the exhaust back pressure valve was activating going down the road at crusing speed. I called the dealership and talked to the service manager and they said it sonded like the diaphram in the actuator valve for the exhaust wastegate (the valve right after the turbo) ma yhave a hole in it. so I took it off and found the seals worn excessive. I put in the seal rebuild kit for the wastegate. now with everything reinstalled it automatically engages at start-up and wont disengage until it is at normal operating temp. when I go down the road at 30 - 35 mph, it engages and wont disengage until I let off the gas pedal for about 5 - 10 secs. I have tried disconnecting the exhaust back pressure sensor and it seemed to help (it lets me go about 50 - 55 mph before it activates now). the dealership says they cant even tell me what triggers the valve. so I am asking for any help that anyone may have concerning the proper operation and sensors involved that I may be overlooking. also, I have had the engine wireing harness, fuel pump, injector pump and injectors replaced trying to help diagnosis this problem.