Disconnecting the line stops the wastgate from starting to bleed off boost early, they are set to start bleeding at about 5 psi. Shortening the rod lets the wastgate go to a higher boost before blowing off, so you spool up a little faster, and can achieve a couple of lbs more boost, makes up for the drop in boost from the stock to WW. Not really recommended without a boost gauge, and helps to have a boost fooler on the map.
Gord.