http://www.lcengineering.com/
http://www.urdusa.com/
Nothing wrong with the 4 Cylinder! It's a stout little motor that will last forever.
There's probably Turbo Kits for it. But doubling the HP would require a complete motor teardown and rebuild. You would need ARP Head Studs, new Crank, Pistons, Connecting Rods, etc.
It would cost you a pretty penny to do all that, then Turbo it.
But if you google around I'm sure you can find a Turbo kit in the range of $3,000-$5000 that will give you a nice boost without needing a rebuild.