It seems the 2014 Audi S3 is facing some problems with the turbocharger of the 4-cylinder 2.0-liter engine. Apparently, the Volkswagen Golf R and the Seat Leon Cupra suffer from the same issue (engine code CJXB, CJXC) and the part to blame has the code “06K 145 702 N”, with the component being manufactured by IHI Turbo.
Most of you know that all three cars share the same MQB platform developed by the Volkswagen Group which also underpinned the third-gen Audi TT and the latest Skoda Octavia. The mounting points for the engines are the same among these cars and so should be the distance between the front axle and the firewall.
It should be mentioned the Golf R and S3 come with all-wheel drive and 300 PS whereas the Leon Cupra has a front-wheel drive layout and packs 280 PS. The problems occurred are probably related to a small batch of turbochargers produced in April and May, but some owners of the 2013 Audi S3 also complained about this problem.
In the 2014 Audi S3 and the Golf R and Leon Cupra, the problem apparently has to do with the manifold sealing surface but a confirmation on this piece of information is not available at this point.