hi who put the head back on the car and connected every think up as it might be a simple thing as loose connector i would start with removing all connection leads check them and clean them and give em a little spray of wd 40

then check all the boost pipes and the inlet manifolds and gaskets and make sure all the nuts/bolts are tight

i take it as you put your foot on accelerator it cuts out which could be a air leak so check the easy stuff first

does the car idle for as long as you dont touch pedal

was the car fine before the head was done
are all fuel lines in correct position
mark2