I am wanting to do this to my ls mounts and just wanted you feed back on it before I do it thanks Nate here is the link http://importnut.net/motormount.htm.

 

My tuner did something like this on his eg hatch, and said it was quite an improvement. Instead of injecting that stuff in though, he just took a bunch of different sizes of rubber tubing. Basically cut them length wise, and rolled them up so they were nice and solid, then shoved them into the mounts. Its a cheap fix, but it gets the job done