Dedicated server config advice sought…

I have two sites. All the same files, exact same database: the slow site was EXACTLY copied from the fast one. It seems it has to be in the server configuration. The slow one is on a dedicated server with 16 gig of ram and 8 cores. The fast one is on a vps with 1 gig of ram and 1 core. Anyone have any advice on fine tuning my slow dedicated server site? It’s centos6.6 with plesk 12, php 5.6 and mysql 5.5.

These are the sites, check out the speed difference with a category (state) selection:
Fast: ffl.firearms.center
Slow: ffls.firearms.center

Any advice for server config on a Directory theme with a large database would be really appreciated.

Thanks,
Bob