Just had a look at the specification tables I put together.
The 4/4 front and rear track increased in 2000.
So 1997 to 2000 was narrow track. From that point, the front track increased by 0.75" and the rear by 0.25".
Coincidentally the Plus 4 ceased production in 2000 for four years, and one might speculate that this also had an impact on 4/4 dimensions. There would likely have been some Plus 4 components left over at that point.
