1986t-bird help dont know what to do

I have a 1986 elan 5.0 runs smooth for 2 wks at a time then starts to diesel and knock then shuts off.I let set for15 to30 mins. then it starts up will run good for 3 or 4 days then the same thing over and over again I have replaced fuel filter 2 injectors throttle body sensor fuel pump coil a cople of vaccum lines o2 sensor just 1 (havent changed the other one yet) emission valve ignition switch still doing the same thing. I tuned it up about 6 or 8 months ago dont know what to do I am very desparate somebody help please

Where is your timing set? Is the TPS putting out the right voltage at closed throttle? Might be worthwhile to clean the EGR passages while you're in there.