Try these links: http://forums.pelicanparts.com/porsche-911-technical-forum/545165-88-911-bumper-removal.html

https://www.porscherepair.us/porsche-911-1984-1989/front-bumper-removing-and-installing.html

https://www.youtube.com/watch?v=dy37bekQq9s

My story:
http://forums.pelicanparts.com/porsche-911-technical-forum/782003-el-chup-tough.html

Bumper, go to ends of front center rubber near the turnsignal, there are little screws, remove them and peel the rubber out of the channel. There is no magic involved in this project, getting the gaps required a little fiddling, use plastic wedges to move the panels after installing but not tightening.