it is your call wether it is too loud or not - but it is loud. I certainly wouldnt consider running it inside, It is bearable in a garage with the door open, but I only do that when fiddling - I certainly wouldnt want to have it sitting there for the 30+ minutes per tank you will have for breakin.

I broke my savage in on a summer afternoon, at first I set it up just near the back door so that I could sit in and watch soem telly whilst keeping an eye on my truck. but it was so loud i moved it to the end of the garden so it wouldn't bother me as much...

also be aware that beause the settings for breakin are so rich there will be lots of oil dripping out the exhaust, so put something down to catch this...

Start it up and make your own judgement call. If you have an empty house and live on a farm then who cares.... but if you live in a Semi in the burbs, expect complaints!