McLaren is testing the front exhausts

Today, during the Jerez tests, McLaren took the MP4-26 onto the track equipped with a Renault-style front exhaust system.

According to Auto Motor und Sport, the car that debuted on the track with Hamilton is therefore different from the version presented last Friday in Berlin.
There had been rumors that McLaren would bring a new exhaust system to the track, after Kubica set the fastest time in the Valencia tests driving the R31 equipped with a similar system.
The Auto Motor und Sport correspondent in Jerez claimed that the conventional exhaust system at the rear had mysteriously disappeared by the time Hamilton left the pits on Thursday morning.
Now the exhausts come out in front of the bellies, and the change only became apparent when the mechanics, who were pushing Hamilton's car into the garage, had to stop.
“As with Renault, it is very difficult to photograph this detail,” writes the German publication.

Filippo Ronchetti