Noise - vacuum or exhaust?

[slo95]

I installed a Bassani cat x and mac cat back to stock headers a few weeks ago. I noticed a slight almost kinda "whistle" when accelerating. not at idle, and more so under load. It does get louder as speed increases. Not a chirping or ticking sound though. Just a constant low pitch whistle.
I finished it up last weekend with motorsport headers. Noise is still there.
I lined everything up three times - tighened with a very nice air impact, so much so that I snapped a collector bolt. not fun.
So, does it sound like an exhaust leak? I swear the 400ft lbs at 125psi does not turn the nuts anymore - so they are tight (that and I have reinstalled it 4 times now).

What are the most common vacuum leaks -
it almost sounds like the Idle Air Bypass when it is open too much - like that type of air rushing whistle.

[PKRWUD]

With the engine idling, disconnect a vacuum hose and see if the idle changes. if it does, you do not have a vacuum leak. If the idle remains the same, you do have a vacuum leak. The easiest way to locate it is with a propane torch. Turn on the valve, but do not light the torch, then guide it around any place you suspect the vacuum leak. When the engine idle increases, you've found the spot.

Take care,
-Chris

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[slo95]

I will try that, i tried the starter fluid trick last night with no success. I disconnected a few vacuum lines, only on the smog stuff (EGR and those regulators on the hoses) and FPR and idle did not change.