Toso studied automotive design and electronics at Apeldoorn Technical College, followed by a degree in automotive engineering. He then obtained his masters in aerodynamics and flight at Cranfield University in the UK. He worked in the Dutch national aerospace laboratories until 1995, when he was recruited by BMW for its GT racing programme. In 1997 he moved to the Jordan F1 team, where he worked as a race engineer. His time at the team included its first win at the 1998 Belgian Grand Prix, where he engineered driver Damon Hill's victorious car.
For 2001 he followed former Jordan colleague Mike Gascoyne to Benetton, which had been sold to Renault the previous year and was rebranded as such in 2002. At the end of 2003 he replaced the departing John Iley as Chief Aerodynamicist, and held this position until June 2008, when he left due to ill health. His stint with Renault included the team's back-to-back Drivers' and Constructors' championships in 2005 and 2006.