MP9 Fuel Injection Conversion

Hi Guys, I'm calling for help from South Africa. I have had someone do a MP9 Fuel injection mod to my '83 1800 MK1 GTi. My problem is that I am getting really bad fuel consumption, roughly 350km per 55litres. I have had a Dastek Unichip installed piggy-back to the stock ECU, however this hasn't helped much. I need to know what all else I can check to get my consumption better. Suggestions have been, get the 1600 Polo head re-CCed to 1800, and get a big valve gas flow, check the injector size (what should it be anyway?), change the fuel pump (still have original in place), install airflow meter and lambda sensor (apparently not required on this model injection). I am getting really confused and would appreciate any genuine help I can get.

Thanx