VS2012 - Intellisense fails with existing C++ code

Hi,

I used to work with VS2008 as a code editor since very recently. We are using libraries such as Petsc and Slepc which prevents me to compile our code in VS. However, Intellisense of VS2008 more or less tolerated that. Now, I switched to 2012 and Intellisense does not work at all with our code (it does work with sample projects). I tried several different ways: converting an existing VS2008 project, creating a new one and add the source files, all the same... Is there a way to inherit the working Intellisense of VS2008 into the VS2012? Thanks.