GMC Repair: Vacuum problem 2002 Yukon Denali 6.0, mass air flow, yukon denali

Question
I think this is a vacuum issue, but I'm not 100% sure. I'm pretty decent with fixing stuff, but this one has stumped me to no end. The truck has about 60k miles on it, and its been having some issues. Occasionally when driving, the voltage dropped a couple points and the lights flickered, but more problems developed. Recently, the check engine light has been going off and on. Its throwing something in the range of Mass air flow, and MAP. This has led me to believe its more vacuum related. It also makes a high pitched whistle when under acceleration. It will also occasionally surge while idling. Any ideas without spending tons of cash on fixing sensors that may not be broken? Thanks a ton.  

Answer
Hi
To assist you with the SES lamp, I'll need the exact code numbers as each of the sensors you list set multiple codes.
As far as the whistle noise here is a bulletin from GM for a 2002 GEN III engine (4.8. 5.3, 6.0)
The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:
Some of the vehicles listed may exhibit a whistle noise from the throttle body area during light acceleration if they are equipped with a GEN III engine and an electronic throttle body.
Recommendation/Instructions:
This is a normal noise characteristic that could be experienced on these vehicles if they have an electronic throttle body. The same intake manifold design is used whether the engine has an electronic throttle body or a mechanical throttle body. Due to this, electronic throttle body engines still have an IAC passage in the intake manifold. The whistle noise may be the result of an airflow disturbance that can occur as incoming air contacts the unused IAC passage.

So if you would please follow up post with the code numbers, I'll be glad to assist you.
Good Luck
Pawl