What do LCA's do?
 

I am buying bolt-on SFC's and they bolt onto the LCA I beleive, so while I am at it, I am wondering if I should buy LCA's as well, and if so which ones. I do not plan on lowering the car. Its an A$ if that matters.

What do the LCA's do?

Are they worth buying if I do not plan on dropping the car?

Are they worth it for an A4?

they help reduce wheelhop,they're usually cheap or you can just box your stock ones

LCA's are designed to positively locate the rear axle in a fore/aft orientation. I can't tell you if they're worth it for your application, but aftermarket LCAs will eliminate much of the flex from the stock pieces as well as the slop from the factory rubber bushings. How stiff they'll be depends on what kind you buy and that depends on what you need for your application. Try searching. There is a TON of information on LCAs in this forum.

LCA's will "steer" the rear around turns for those of us that like the twisties.