2005 baha ss surging idle and no throttle

[sadburu2005baha]

Hello I have a 2005 subaru baha turbo I just rebuild the engine and popped it back in when I started it it is surging between 600 and 1200 and even with the throttle to the floor nothing really happens just a slight increase in idle speed. Any idea what this could be I believe everything is plugged in and correct car ran before I took out the engine i was just doing a bunch of preventative maintenance.