i bought myself a a front strut bar couple days ago.
so well im just wondering if there was any rear strut bar available
for a 1999 Audi A4 2.8L V-6.

 

I've never seen one, probably because of the fact that unlike the fronts, the struts don't mount on a horizontal plate or surface where a bar could mount. There really isn't much in the trunk that would allow you to bolt one up.

 

There a few threads on Audizine about MAKING one but looks to meh for the efforts

 

Honestly since the car is a three-box design I doubt a rear bar would do all that much. I doubt a front bar will do much either really - the secondary firewall will basically do the same job.