General Tech Help - won't idle

I own a 89 civic si. I just rebuilt the top of the motor. as long as it is not idling it sounds great, once i try to let it idle it stalls or is very irratic could my timing be a little off or maybe my MAP sensor, i'm stuck someone please help!

The timing could be the problem. That would be the firts place to look...

^^^^ i agree :) also double check your vacum lines. was there any valve adjustments done after the head was rebuilt? an old v8 trick for more hp is to run tighter clearances on the lifters. when you close the valve lash tighter it will cause the car to not idle properly, something to thinnk about.