Derek did a step by step here:
http://www.fto-ireland.com/forum/phpBB2 ... n&start=25
ALso this from mivec.co.uk
Q. The front grille is very rusty and I want to clean it up - how do I take the bumper off?
A. Thanks to Josh Swinnerton for this answer:
1) Under the bonnet, unbolt the two metal strips which go from the bumper back to the chassis, just above the radiator (they're right on top, easy to access).
2) Under the bumper, remove plastic screws/lugs from the two plastic strips that go from the bumper back to the chassis. They're quite big and plastic, and are a part of the bumper (hence the same colour as your car).
3) At the front edge of each front wheel arch, remove the screws to release the front part of the mud guard. By mud guard I mean the black plastic casing around the entire wheel arch. Remove a few of the screws at the front to access a vertical screw which goes from the bumper up into the bodywork, right at the end of bumper. Its at the point where the line between bumper and front left body panel meet the wheel arch. Get a screw driver up there, and release this screw. (if you can't see it, get a light under the car). THIS is the only tricky bit.
4) Now simply remove the four main bolts which hold the bumper on. They're under the car, along two rails which face forward on either side of the engine. You should now be able to carefully slide the bumper forward. Before removing the bumper, disconnect the plugs to either fog light - there's one big plug for each.
there may be some more info here too:
http://www.mitsubishi-fto.org/