I've had a little bit of experience with FOA, so I'll share my thoughts. A good friend of mine has been racing on them for three years. They can be made to work, but you will have do a lot of work to them yourself. Don't rely on FOA.
First off, like everyone else said, they leak. We had one shock that leaked on the trailer before it ever saw any dirt. The first time I actually tore one down and saw the internals the problem was obviuos. There was aluminum shavings all in the oil. At first we thought it might be something broke that caused all the debris, until I looked at the new internals that FOA gave us to rebuild it with. I'm a machinist by trade, and I would be ashamed to have my or my shops name on the machined parts that FOA was using. It looked like they had the local tech school kids building parts for them.
It was obvious that whoever did the machine work made no attempt to deburr anything. This was the source of the aluminum chips that were in the oil causing problems. The threads had huge burrs on them that would break off and imbed themselves into the seals on the piston. In turn this scars up the bore of the shock body making it trash and putting even more shavings in the oil. The internal o-ring grooves had sharp burrs that would cut the O-rings that seal the shaft causing leaks. Also, the surface finish was nowhere close to spec for an o-ring groove.
In order for them to work you need to tear them down when they are brand new and go over all the machine work to clean it up. I can't comprehend why FOA couldn't figure this out.
On several occasions we had the end blow out of the external reservoirs.
If you want them tuned, double check it yourself. Check to make sure you have the correct shim stacks in all shocks.
However, I will say that all of this was on the old style shocks. I haven't personally seen the new design, but FOA claims to have resolved these issues.
Shocks are expensive. I would take everything into consideration before you make a purchase.