This worked for me, just a short threaded 3/4"x 2" PVC nipple with an end cap.
I threaded it slightly into the spark tube and with a bit of wiggling out they came without removing the spark plugs first.
http://986forum.com/forums/attachments/diy-project-guides/20616d1482167501-spark-plug-tube-removal-tool-spark-tupe-tool-1.jpg