From my FB page:
"It appears I may have reached the limit of the OEM clutch. Keep in mind, my Fiesta ST has 52K on the clock, but as I push its limits more and more every day, I think it finally gave in.
I recently addressed some boost leaks that were discovered as boost pressure was increased near 29 psi. I fixed those, and took the data logs that are in the attached VD. The clutch held consistently at this power level and didn't skip a beat. But when boost pressure was raised slightly over this, the clutch started slipping.
I may go with a reverse boost taper, which is something commonly done in the Mazdaspeed platform. Keep boost tame near spool up (to control the slip), and then give it hell as RPM's increase. I may give this a shot, but at the end of the day, I need to replace the clutch.
Drop your suggestions on a replacement in the comments! I'd love to hear your experiences and impressions of overall drivability and feel for a somewhat-daily driver."