I put a aftermarket sub behind the driver side seat and it vibrates to much - is there any way of getting rid of that - i really dont want to put the sub in the back of the car

 

Well, to fix the vibrating, you can use a lot of sound damping. However, look around this forum for a while and use the search function. You may soon find out that using the stock sub location may not yield the greatest results. It's not a sealed enclosure and it takes a LOT of work to seal it air tight. Good luck!

 

Play The Beach Boys greatest hits, see if Good Vibrations fixes it.

 

What is vibrating? If it is the panel it is on surround the edges with dynamat.