...and just as Pimpernell mentioned...using lots of PB Blaster and taking lots of time is the way to go. It took me 3 days to get two out of a friend's '99, working with the engine hot and turning maybe 1/8 rotation back and forth for the first two days. Learned my lesson on our car!

Too late here but for those who encounter a stuck but not yet broken plug... take your time, soak it, heat it, walk away when the urge to apply more force strikes you... Repeat for a few days if needed. Once I got them past the threads they were still stuck. I started the engine (make sure there's nothing loose to get sucked into the intake ports!!) and the compression blew both plugs out immediately.