How can I more optimize My AI Script

Hi, I was studying for a month Unity3D, and Make tiny FPS Game. (After make the FPS Tutorial)

I write all script to C#, and I think good to run.

But, When I play my game on my second-PC , It make lower 10frame per second.

http://pastebin.com/hc3KyENC

here is my AI code.

How can I optimize this code.

Plz tell me technic of optimization.