Something is really wrong with my idle/throttle response. It seems
Like my car is running lean. When my cars idle finally settles down, it's idling at 500-700 RPMS.. And it's causing horrible shaking of the car. Also sometimes when in 3rd gear just cruising it like bucks for a second or two.

Someone suggested I might have a vacuum leak, because at around 4,000-5,000 rpms you can hear whistle/hiss.

I don't know if a vacuum leak affects throttle and idle response? What could be causing my car to idle so badly low? And can a vacum leak cause bad idle or throttle response?
The intake set up is
BBK Cai, 75MM throttle body, Trickflow Elbow, and Comp Cams intake manifold. Stock MAf

 

Is this the same car that was "roaring" last week?

 

My vote is in for getting the throttle bottle and MAF cleaner. Solved my idle issue and was a cheap fix. If you haven't done this recently I would definitely get it done anyway.

 

The IAC may need cleaning.

 

Vacuum leaks cause high idle, not low. Your problem sounds like a bad fuel pump or clogged cats.

 

Yeah it sounds great lol. The idling is just my issue. For some reason whatever is causing it to idle so low is making it louder at idle. But she does roar

 

Are you running this manifold? http://www.compperformancegroupstore...Category_Code=

That thing will kill all low end torque with those ultra short runners.
They work better with a turbo or supercharger.
How far open is the throttle blade at idle?