Funny thing is I did have an inspector look at the place and didn't
find anything wrong with the plumbing. Only thing he suggested was to
cover up the pit that's collecting the overflow since it located under
the addition where the back of the old house used to be. I think he
sucked as an inspector and Im considering talking legal action against
him if thats possible.

Anyway, my gutters are feeding into some drain and is going under
ground. Does that usually lead into the city drain before or after my
house? In other words, if the city drainage is slow, would the water
coming in from the gutters be trying to go out and not have anywhere to
go but back into the basement? I had the main drain rodded out and I'm
wondering why water still decides to back up during a storm when I'm
not flushing toilets or doing laundry. Basically, Im not adding any
additional water during a storm from within the house.