If by shims, you mean these...
http://www.gtfactory.jp/cms/e107_files/ ... 030255.jpg ... then yes, they DO work and they DO increase steering angle and lock.
Like you already said, they initially increase the track width of the rack. Yes you will have a change in toe after installation, but with an alignment and toe correction you'll still have an angle increase. This is possible because the spacer spaces out the bulky part of the inner tie rod that hits the rack at lock. When the wheel is turned, and the rack is moved, the spacer will tuck inside the rack allowing "X" millimeters of extra track before the inner rod hits the rack, therefore increasing angle at full lock.