After the 2004 season Lieb commenced studies in engineering at the University of Applied Sciences in Esslingen, combining his education with a reduced factory programme with Porsche.

Lieb had previously studied automotive and motor engineering at the University of Stuttgart for two semesters before choosing to focus on racing.

Lieb completed his degree at Esslingen after seven semesters of study and has subsequently combined his racing with a role as an engineer at Porsche Motorsport's workshop in Weissach.

[1] In 2005 Lieb returned to the FIA GT Championship where he won the GT2 Drivers title with Mike Rockenfeller for GruppeM Racing, netting a class win at the Spa 24 Hours along the way.

In 2009, Lieb teaming up with Richard Lietz in the Porsche 911 of Felbermayr Proton in the European Le Mans Series.

Lieb and Lietz successfully defended the drivers and teams titles of GT2 class in the 2010 Le Mans Series, with three wins against two semiofficials' Ferrari F430 of AF Corse.

Also, he earned his second victory in the GT2 class at the 24 Hours of Le Mans, once again alongside Lietz and Henzler in the Porsche 911 Felbermayr-Proton.

Returned to the 24 Hours of Spa as Prospeed driver, accompanying Marc Goossens, Marco Holzer and Westbrook in a Porsche 911 GT2 class, in this occasion the principal during the race, but abandoned.

Counting with Henzler as third driver for the fourth consecutive year, finished 4th in the GTE-Pro class at the 24 Hours of Le Mans.

No raced Petit Le Mans, although in the 24 Hours of Daytona, where he finished 6th in the GT class in a Brumos' Porsche 911.

He also returned to pair with Alex Davison, but this time at the invitation of V8 Supercars to drive a Ford Falcon in Surfers Paradise Grand Prix, he finished 23rd and 18th in each race.

On the other hand, ran in the 24 Hours of Daytona with Brumos' Porsche 911, and the three rounds of minimatch resistance of V8 Supercars Holden Commodore with Jonathon Webb.