Those of you who have an M6 this is a GREAT mod! This all started when I put my Spec III in about 2months back. After installing the slave cylinder on the transmission I obviously needed to bleed the system. Well long story short the clutch pedal wasn't returning. After giving up on the bleeding I decided to start the car and everything SEEMED fine. Well a few weeks go by and occationaly the transmission would grid when i put it into 1st whereas b4 this never happend.
After taking the master cylinder out I noticed the resivor hose was barely attached. I knew it had to have been sucking air into the system while trying to bleed before. Well after modifying the master to make it adjustable I bleed the system and it was 1,000X better. Now the pedal is SOLID, not spongy and I can adjust it to exactly where I want it!