The first changes will come to the Versailles-built C3 R5 in time for Vodafone Rally de Portugal (30 May – 2 June), where revised rear geometry is due to be introduced on the car which has won two WRC 2 Pro rounds so far in 2019.
Østberg, who scored a debut win in the car at February’s Rally Sweden, said: “It will be a proper update coming.
“I have tested this for three days and it’s good. It’s also really positive that Citroën is so motivated and really behind this work for the future.”
Østberg’s second victory came at Xion Rally Argentina, but his hopes of taking the WRC 2 Pro lead at the following event were scuppered when he suffered a rear brake problem at Copec Rally Chile.
The Norwegian sits second in the standings, five points shy of M-Sport Ford World Rally Team driver Gus Greensmith.
Citroën Racing team principal Pierre Budar said development of the C3 R5, which first ran in the World Rally Championship in March last year, was an ongoing process.
“The work on the (rear) geometry will be a step,” said Budar. “It’s quite significant. There is more planned, we are working in areas like the engine and the suspension, but it’s not sure when these changes will come.”