Porsche first quarter 2019 sales fell 12% year on year to 55,700 vehicles.
The automaker blamed the changeover but noted Cayenne demand was up 35% to 18,310 units. The Macan remained top model with 19,795 sales.
Europe sales fell the most, by 32% to 14,004 units, Germany was off 28% to 5,557 and China down 10% to 16,890.
"2019 has started out challenging for us and for the entire automotive industry," said sales and marketing chief Detlev von Platen.
"The changeover to the new WLTP test cycle and gasoline particulate filters has continued to occupy us in the first months of the year. In addition, the unusually strong start to 2018 meant that a comparatively weaker first quarter was to be expected."
Macan and 911 model changeovers also limited sales.
On the other hand, Porsche saw 8% growth in US to 15,024 units, second only to China for volume.
The automaker said the Chinese slump was due to weakening overall market and customer reticence in expectation of the announced lower value added tax rate as from April.
Nonetheless, for full year 2019, Porsche expects a slight overall increase in deliveries supported by demand for the new products.
"In particular the eighth generation 911, which started being delivered in Europe a few days ago, is in high demand from our customers, and allows us to look optimistically toward the future," said von Platen.
A new Cayenne Coupe will be in dealerships from May and, in September, the electric Taycan arrives.