As far as i know, you're supposed to leave the shafts in other wise you won't have any oil pressure and you can kiss your car goodbye. You're supposed to remove the chain and tensioner. After the tensioner is removed you need to get the tensioner delete kit from GS. Here is the linkI've got a 99 9-5, balance shaft chain failed. I've got plugs for the shafts, just not sure what needs to stay or go from the rest of the system. The lower gear seems like it needs to stay for spacing, what do you do about the tensioner?
IIRC, Nick from GS milled some aluminum shaft inserts to replace the heavier stock ones. I think the weight reduction was so minimal it made no difference in performance.When you said you have plugs for the shafts, what is that? That's the second time I've heard of it, but I did not see it on gs website.
You would want to plug off the oil supply to the balance shaft somehow, or leave the shafts in place.