I see the difference in the maps.  But I can't do anything until Google updates their imagery.    Looks like they last updated in 2012.  That shows what I drew.

Hi! I'm from Porto, Portugal (Oporto if you prefer).

I'm writing to express my thoughts about a very odd issue.
Please, try to separate the large layout from the small one (not from the drawing, but from time itself). The Circuito da Boavista was held back in the 50's every 2 years. It had the last large event held at 1960, the event was never held again until 2005 when it revived by the city Mayor.

Back then, the layout used had a length about 7km. Upon it's revival, the layout was shortened around 3km. The confusion resides on Esplanada do Rio de Janeiro. The layout is completely wrong, it used to be a straight, now it's curved because the area was recently rebuilt precisely to create a larger esplanada and beach area.
There seems to be a lot of confusion over the hundreds of layouts I've been able to visualize, and most of then tend to misdesign this particular arror, like you did.

currect layout: http://pt.wikipedia.org/wiki/Circuito_Urbano_da_Boavista#mediaviewer/File:Circuit_Boavista.png

Keep it up!