RATTLING NOISE EXHAUST PIPE/BACK OF ENGINE

[joeljcruz86]

HELP!

I've read through the forums related to this issue and still no success. I have a weird rattling noise that comes once done within the following:
1.) driving the vehicle more than at least 15 minutes
2.) the car is in drive and the foot on the brake pedal

The rattling goes away when in neutral, and it isn't there in reverse as well.
The sound is very strong behind the engine bay and the noise goes with shaking the engine back and forth by hand. My friend and I noticed that the noise also went away when a flat head screw driver is wedged between the mid-pipe connected to the up-pipe (headers) towards the engine. I also pushed up (braced) the mid-pipe towards the bottom of the car and the engine goes away too.
My friend strongly feels and convinced that my gasket that connects the two pipes is most likely bad and that there is an exhaust leak possibly. but the car does not sound like it has one.

I drive a 2009 3dr. hatchback, aftermarket exhaust, over 100,000 miles.

ps. I also tried the zip-tie of that cable method and it is still there. Plus checked most of the head shield through out the exhaust pipes and still nothing.