hey guys just got my d15 vtec head into my d15b7 block fired it upbut now it pulses from 1200 to 1300 rpm any ideas

 

Did you reconnect all of the vacuum hoses? Try cleaning the FITV and IACV, and bleeding the cooling system.

Any CEL codes?

 

Do what Ron says, but if that doesn't help then:

Spray some carb cleaner between the head and the intake. If the idle fluctuates you have a leak at the gasket.

If that doesn't change, you can spray (lightly - don't hose the engine bay) over other vacuum lines and listen for it to change. Quickest way I know to pinpoint a leak. Second, more safe alternative is to un-hook vacuum lines one at a time.