vibration during deceleration /misfire at idle
 

01 Boxster 5 speed 21k miles

My friend asked me to check out a vibration/rumbling noise she had in her boxster while decelerating.....thats all the description i got.
i was frustrated when i first took it out because i didnt notice a thing, but then well into the drive i started feeling what she was talking about from around 3200 - 3000.

now i read a post that claimed a muffler adjustment would fix the problem and before i started messing with it i wanted to see if there were any other opinions on it.

and unrelated: the car very rarely has a misfire at idle, i can't really seem to pattern when it happens because it hasn't happened enough.......just wondering if theres a common problem.........no codes when checked.
thanks.

sidenotes:
the muffler theory is given some credibility by me because i only get the vibration when the car is warmed up, which makes sense with how much that metal expands

and the other things i could think of that cause that vibration would include clutch/flywheel imbalance or a cv joint on its way out.........and all of those would produce vibrations no matter how warmed up the car is.

Have you considered checking out the motor mount located inbetween the engine and the firewall behind the driver seat?