Explain "using shitloads of fuel".
Also explain "half power"
Both these terms are qualitative, not quantitative.
It should not be the air flow meter, because Blacktops are MAP sensored. You should have no AFM.
O2 sensor can send your fuel out. Map sensor leaky.
Are you running 98 RON fuel in it? Knock sensor can pull timing if it detects too much knock (low RON, dead sparkplugs, dead ignitor, many things.)