Hello. I have an issue that is about to make me pull my hair out.
Driving or giving the car any amount of gas at all there is no noise or vibration at all.
When I stop at a red light the car starts a mild vibration. The whole center console and floor pan seems to be getting the worse of it. This vibration varies between a massage chair and a roll-a-coaster.
Back on the gas and the vibration goes away.

Put the car in reverse (not pushing the gas pedal) and the car feels like it is going to fall apart. Gas - no vibration.

I have spent countless hours trying to find this. Headers are no way touching anything. Exhaust pipes have plenty of clearance etc.

Any thoughts? This has been going off and on since I have owned the car - bought new. It has recently gotten to the point of insane.

Thinking of trying to find a nice dealer and having them check. I do have JBA headers and motor mounts.

Also this is not a noise like something is hitting. It is a pure vibration.[/align]
Tonight I figured something out 950rpm or so and up there is NO vibration and the car is running great. "
500-700 is a horrible vibration 800-900 substanial vibration.[/align]

 

its probably wanted to shut off at that low of idle....keep it above 750 is best

 

Its a V6 and even before it was tuned it idled around 550.

 

I also think the idle speed is too low. But is it possible that one of your motor mounts, broke during the header install.

 

does it kind of come and go? cuz i JUST noticed this with mine. when im in park, or in drive but at a light it comes and goes but its a very faint but noticable vibration. it just started happening and i have 50K on my car.

 

and my idle is at about 1K, a little bit under. Also the vibration isnt as bad as yours, i can only feel it in the shifter and kindof on the break but i thought it was just me being paranoid and over protective about my car lol

 

Installed new prothane motor mounts yesterday. Drive vibration / clunking etc is gone and the car is awesome over 1000k. Mounts helped.

I know they are not making this any better, but I think it is fair to say they magnified a vibration that was not supposed to be there.
This vibration has been going on for a while.