First time I ever heard of runnining a line from front drivers side bleeder valve back to M.C. hey might work never tried it. Rocket I had a strange pedal too with the symptoms you describe, I first tried a good bleed on the system hoping that would correct it but it did not changed the symptoms a little but did not correct it. I bit the bullet got a rebuilt M.C. carefully bench bled it seemed I was better if I went a little shorter then full stroke with the plunger if I went full stroke I would reintroduce new air in system. Got all air out put it on and pressure bled with home made bleeder with about 20 psi. on system one wheel at a time checking fluid level in master between wheels and end result was great brakes. I think someone said that if you want to check to see if you brake booster is working is to push pedal down w/o engine running then start engine pedal should rise if booster is working not sure if this is correct or not but is what I have read.