Suggest to perform diagnose at work shop, usually the keypoints of diagnose are:
1. Check the intake manifold if there is crack or damage, replace if it is broken.
2. Check if the intake manifold valve can be opened, replace if necessary.
3. Check if the contact point between the intake manifold and the engine is loosen, tighten the connecting bolt.
4. If the condition is beyond repair, replace the intake manifold.