Having a hard time getting my freshly built LS/VTEC to idle down, when I start it up it revs up to 4,000 and stays there. I a chipped P28 ecu. There isn't a surge either a steady 4,000 and I can rev it too but once I let off the throttle back down 4,000.

 

Sounds like a vacuum leak.
Check your fast idle thermo valve & intake manifold/throttle body gaskets etc...

 

I haven't checked the map sensor yet, is it possible that is bad?