refitted my twin kadrons the other day,finally went for a blast,now got more horses, performance of a gti fuel consumption of a 747,who cares about the planet i get the tax for free anyway,some ye win some ye lose.
Aye - Kads can be a tad thirsty! 
Maybe it’s the sudden urge to boot it everywhere and enjoy the extra grunt…? B)
However, Kads in my Van with a 1641cc motor 10 years ago got me around 23mpg, which was respectable enough, and while shifting 1776cc of air/fuel mix in a Bug I thought 25mpg was OK for the power! 
Do an economy check over a few full tanks of normal driving…