the allen bolts are for adjusting the height of the bumper and arnt meant to come out,[they have a blob of weld on the ends]the proper ones are up behind the bumper,you will see 2 bolts in each chassis rail,remove rear ones loosen front ones,twist the plastic side ones as mentioned above and the bumper will pull out complete with mounting brackets[assuming of course that youve disconnected/removed fogs/indys etc]
