Re: Should I replace my toilet or use an auger
Try holding the flush handle down for more water when you flush. If that takes care of the problem then it's probably a poorly designed low flow toilet.
It could be something in the soil pipe or a blocked vent. Check and see if any of the plumbers in your area have a snake cam. He can lower it down the vent pipe and see if there is blockage in the vent or soil pipe.
Replacing the toilet only takes a few minutes so if you're adventuresome you could swap toilets and see if you then end up with the same problem in the other bath room.
Be sure you live your life, because you are a long time dead.-Scottish Proverb