Check your fuel system. Make sure there are no air leaks, cracks in lines, etc.... Also make sure that your pressure side of the fuel system is not cloged(or any part of the system). If runing a fuel filter.. make sure it is clean.

Also.... setting the low end before the high end needle will do this to. If that is the case.. back out the low end needle and set the high end needle first. Once you have the top end set... then go for the low end.