04 Mustang engine flutter?

My son's 04 Mustang 3.8L V-6 is making a fairly loud fluttering noise comparable to an exhaust leak, which I had thought it was.
Upon starting cold, it really makes some noise, I checked the exhaust system and when the engine was started, I followed the noise to the engine itself, up to somewhere around the a/c compressor (was energized/clutch locked on)then as the engine ran the noise got progressively quieter to the point of very little/none. Could it be something with the air emissions equipment. I don't think there is an air pump on this late model car but that is what I would think it was other than the exhaust leak that I was hunting.
One other oddity is there is a section of black fuel/gas hose near the automatic trans. dipstick that is deteriorating badly, very chalky(black residue), the hose goes into the fuel throttle body right behind the what looks like a TPS or other sensor on the air intake body. The hose is marked fuel/gas hose, I would like to replace it soon due to the deterioration. If it carries gasoline it could split/rupture. Also, I see the bad hose section connects to another hose section with a plastic type coupling/union. Can somebody explain what hose this is, could it be a fuel return line? And can it be replaced easily?
Thanks guys, always needing your great assistance,

Response:
check your Cat for a tube coming off the side, follow that tube if not capped off at the cat, to a diaphram valve assy. where it connects to a rubber hose. I think you'll see the problem.
Now the fuel line could be either pressure or return and they are braided which is why there's a union. There are 2 types, 1 uses a special tool like A/C unions. The other has a plastic clip that usually breaks and cost $.15 from most Parts Outlets. But they generally run up the frame rails away from the trans.

Ford to offer 'mayhem' performance package to Mustang option list

The social networks have spoken: The Ford Mustang V6 performance package will now be known as the Mayhem Mustang package.

Ford put out a call to its 1.4 million Facebook fans with the question, "What should we call the Mustang V-6 performance package?"

More than 3,000 submissions were made via Ford's Facebook page, and almost 6,700 users installed the "You Name It" app. The winning submission came from a fan in North Carolina, who won a three-year lease on the 2012 Ford Mustang V-6.

The five names that received the most votes were selected, but Ford made the final decision. Each finalist was run through trademark, copyright and brand approvals to make sure the no toes were stepped on. The Mayhem name will be used on all of Ford's marketing and communication materials.

The package combines the base 305-hp engine with a 3.31 performance rear axle and Mustang GT-based suspension and braking parts. The Mayhem Mustang gets unique 19-inch wheels and Pirelli performance tires. Other highlights of the package include:

Mustang GT front and rear stabilizer bars
Mustang GT500 rear lower control arm
Strut tower brace for increased body rigidity
Unique electronic stability-control calibration with sport mode for performance driving
Unique badging
The 2012 Ford Mustang V-6 stickers for $22,995 with transportation. The Mustang Mayhem package adds $1,995.

my car will cut out while driving in all gears at all rpms

Question: I have a 1994 mustang gt 5.0L 302, my car will cut out while driving in all gears at all rpms and when i push the clutch in it will rev itself to over 2k rpms and wont drop till i tap the throttle then when it drops it will only drop to 1500 then will drop to normal when i am stopped idling for 15-20 seconds. Already Tried: I cleaned the idle air control motor Answer: This high Idle is a classic description of a vacuum leak. Most common place for the leak is the PCV valve hose located at the back of the engine under the upper intake manifold.