When ever you unplug the battery or unplug the ECU you have to turn the key to the on position for about 30 seconds before starting the car to allow the ECU to do a throttle body adaption.

 

UPDATE:

finally got the car scanned, had error code: open n75 valve.

had a look and the one of the wires connected the n75 valve had been ripped out (my fault most likely when fiddling with the stock air box)

soldered that all up and problem solved! turned out it wasnt maf related!

thanks for everyones help.