One thing I know to check would be whether it's got soft or hard shims under the springs. I bought an early set used and had to change them out to hardened shims - I got them at Summit, same diameter & thickness as what was under the springs.
Some people have put hardened spring cups under there, but then you have to have the spring pockets in the heads milled out larger.
You do want to check that - if the soft ones are run for very long, the springs will chew them up and eventually chew into the aluminum itself - spreading lots of metal debris throughout your oiling system and ruining the heads.
Also, on mine, there were some sharp casting corners protroding into the corners of the exhaust ports. I rounded them out and cut them down quite a bit, figuring they created turbulence and both blocked and hurt flow quality.