Check the TPS. It should probably read close all the time, so when you pass 1500rpm (or whatever rpm is the deceleration fuel cut for your ecu) it will cut all power to injectors and as soon as it will reach ~1100 it will again start firring them. If you have a wideband, it should be obvious, when rpms drop, there should be no or extremely lean reading. Unplug the tps and check again. Also check for vacuum leaks. Finally when it's cold, it shouldn't do it for the first lets say 30-60 seconds.