Hopefully you greased them after installing.

If you installed and lubricated the the new poly bushings properly then your squeak may be from the hood snubbers which you'll find just inboard of each headlight. They'll mate up with the round worn-looking spots just underneath the leading edge of the hood. They're rubber and are adjustable by turning as you would a screw or bolt. If they're out of adjustment that could be the cause of the squeak. Try adjusting them "up" (turn counter-clockwise") to increase pressure slightly against the hood. You can check by closing the hood and seeing how the alignment is with the fenders. If you really have to push the hood down to latch then they're much too high. After adjustment if you still hear the squeaking try putting a little dab of grease or belt dressing on top of each snubber.