Freya's normal dog food and the food she was on when I bought her is Innova large breed puppy. It's a 4 star dog food.

I went to the local petsmart (It's a warehouse dedicated to all things pets) and they didnt have it, they'd never heard of it and said I should never be paying the $175 I paid for it for any dog food.

I looked at a few different ones and settled on the Holistic Select. It's also a 4 star dog food. I paid $130 for 13.6kg

I was just wondering how I should fo about introducing it to her? Do I gradually introduce it with what I have left of her innova or do I use up all the Innova and give it to her cold terkey?

She gets an upset tummy with lots of things. Just the other day she stole the kids crusts off their plates after their lunch nad had terrible gas for the whole night.

If she eats cat food she gets dhiarrea. She hasnt had dhiarrea for a good 6 weeks now. Do you think changing her food will bring it back and how long should it last if it does come back?

If you know she has a sensitive stomach and you still want to switch then I would do a slow transition. If at any time during the transition period she goes soft or to full blown diarrhea back off a little to get her tummy back on track. With sensitive dogs, there's nothing wrong with sticking with what works whether that's Innova or Holistic Select or something else. Just as a personal aside, it's really no one's business what I choose to pay for my dogs' food and my food choices are not governed by cost alone. Back on topic, every dog is different so there is no textbook rules to go by. But common sense rules the day, some stomach upset and possibly diarrhea can be expected, however if it is to excess and/or long term then something is obviously not working. But at least you have Innova as your baseline since you know it works for her if you need to come back to it for any reason.