subitoy

My 3.4L start having some white smoke at cold start up. Recently my engine start to really shake and running rough at start up to the point that it can't idle by itself and needs higher rpm to run for the first 30 seconds. I have minimal coolant loss and white smoke lingers for a while so it's not just a steam. I did block test several times and there is no exhaust coming to cooling system. Seems like the leak at the intake. Not common for 3.4L and I could not find any threads on replacing intake manifold gaskets. Was wondering if anyone has any idea on what other tests to do and how to proceed.
Thank you for your help!