It should not take 2 or 3 gallons of fuel to properly break in an OS  .46. It should take less than a gallon and should be giving you good mileage after just a few tank fulls.  Our club was given 2 Nexstars a few years ago and I was the head instructor. I broke in the engines as called for and neither took more than 10 flights, maybe 60-75 oz of fuel. I still think you have a leak or are too rich.