My 2004 XJ8 has lately been shaking when the weather is warm at the time of startup. The other day the check engine light came on and when I looked at the codes it gave me P0300, P0301, P0303, P0305, P1316 etc. Also when I popped the hood I hear a hissing sound and I can't seem to locate where it is coming from. So does this imply a vacuum leak? If so, can someone tell me what hoses I should be looking at on this vehicle?
Since I am not really very knowledgeable about cars I would appreciate any useful graphics or images that can help me locate relevant hoses in this particular type of vehicle.

 

Some hissing sound is normal from the PCV valve on this engine. However, your codes are for various misfires. This could be a result of a large vacuum leak. The PCV system hoses are notorious for breaking. However, I don't suggest throwing $300 on new parts without proper diagnosis.

First thing to do is remove the vanity cover and look/listen for obvious leaks.