Sauber will bring a rather small update package to the Spain GP, according to AMuS
http://www.auto-motor-und-sport.de/form ... 28081.html.
-ATM, they cannot use the full power of their engine as they are forced to reduce it due to cooling issues. They are working on a new cooling system for the Monaco GP
-They will bring a new rear wing for the Spain GP and some modifications on the front wing
The article, however, somehow contradicts Wehrleins statement in Motorsport, as he is talking about a "big update" for the Spain GP:
https://nl.motorsport.com/f1/news/wehrl ... er-903330/