26 mpg, it's a mystery, suggestions please

[ProdigalSon]

So I always thought my Gen.1 Fazer was a bit thirsty, i expected it to drop a bit after I fitted the Ivans Full Monty kt, ported the inlet rubbers and fitted a high flo filter but I did an 80 mile ride having brimmed my tank. I filled up when I got back and it took 13.64 litres which I make a paltry 26 mpg which I think is adequately described as horrendous. I know it's fuel injected but I spanked a Triumph Speed Triple RS demo today and it still showed over 40 mpg, other than the awful fuel consumption the bike seems to run spot on, ticks over smoothly, picks up revs quickly and pulls cleanly right to the red line on the rare occasion I venture that high up the rev range.
So any ideas oh knowledgeable ones?  :'(