Hero,
Looking at the EPR, look at the back of the mixer and check for part and serial number. If the part number is 1657600 and the serial number has a A or B at the end, the EPR will need to be updated. The one you installed should be good, but better to be sure. If you have replaced the EPR and Mixer, need to know if there are any codes. Sound like something electrical could be the cause. Good Luck.
New epr, plugs, wires, throttle body, unit will only run full throttle, anything less it stalls...
Hero,
Suspect the EPR has failed. Check for primary pressure at the test port. Need a gage that reads 0 to 10 psi. The pressure with fuel tank fully open and engine running is 2 to 4 psi. If all is reading correct, you may have additional damge in the mixer. Good Luck.