when I was in Karachi, the word assembly in Karachi scrap shersha meant a short block, which is an assembled block without head and hanging equipment like alternator, ac, starter, mounts etc.
if this is a complete engine change and its failing to accelerate, Then test each ECU input parameter for normal operation. If you see a cam variator then test its functionality too. A bad variator can upset timing.
In most cases failure to accelerate smoothly on that engine is a bad EGR valve.