Hey folks can anybody help me with this one?

FRST, OFAB, standard, just been put together after replacing the head gasket!

Car starts fine, idles, revs half way but when you give it full throttle the car gently cuts like its getting starved of air or fuel! If you keep your foot right down the car dies, if you let your foot back up half way it goes fine again!

Im thinking this is a ecu or map or o2 adj or tps problem!!!!!

What I know so far is this - Fuel pressure is fine, compression is fine, spark is fine, all electrical readings seem fine, battery is fine, when tps is disconnected it wont even start, ecu is getting live.

Two concerning issues:

Fuel pump feed from ecu reads +4 volts all the time, even when the car is running!

I put new spark plugs in ran it on half throttle for a couple of minutes, checked spark plugs - fine! I then put the spark plugs in and ran it for a minute on half throttle and tried flooring it, it did its usual, i did this twice then switched it off. Took plugs out and they were black - overfueling!!!!!

PLEASE HELP, PLEASE!!!!