94 olds 88 royale

had it diagnosed and brought up codes 401 for egr flow and codes 640 and 670. the codes 640 and 670 as i was told are quad driver modules locate in the ECM. Quad 1 and Quad 4 failed. i understand other sensors and such but i have never run into this problem code 640 and 670. does the ecm have this QUad driver modules in it and do i need to replace the ecm to fix this?

thanks,
tury