Someone needs to go back and read the past posts on doing this mod. The stock WR exhaust cam timing is retarded (13 pins between 12:00 timing marks on ex cam and in cam) If you advance the ex cam 1 tooth you will have 12 pins between 12:00 timing marks. Therefore, you have advanced the timing to near YZ spec.
Actually, this is a misconception started by one of the original magazine articles documenting the mod. While the article had the mod correct, they screwed up on the nomenclature.
When the cam is rotated so that there are only 12 pins, you have just retarded the timing (the cam's rotate top-forward, away from the tensioner).
Advancing the cam timing would entail rotating the top of the cam forward, away from the tensioner.
YZ timing has the exhaust cam closing at about 20 or 22 degrees past TDC. Stock WR timing has the exhaust cam closing at TDC. The mod retards the timing so that the cam closes later, allowing the exhaust pulse to scavenge fresh air/fuel in through the intake valves. This mod also increases the overlap timing.