Chevrolet Impala Engine Vacuum Leak

So, My Car Has A Vacuum Leak Somewhere I Can Hear It Coming From The Back Of The Engine. Could This Cause Power Issues? Like Going Uphill...

I Put A New Intake And Plenum Gasket On Now The Car Has No Power And Sounds Like Its A Squeaking Almost Like Air U Think I Dident Seal The...

Hiss Noise Is Coming From Around Or Below Air Intake Duct. Idle Is Sporadic And With Vehicle In Drive And Brake Applied Car Acts Like It...