I Need Help

We have a 2010 Chevy Traverse Lt
AWD 102,000 miles on it. I was driving
and noticed a whistling, hissing sounds
coming from the car it was very quiet
at first. Then shorty after it got loud & it
seemed like the car didn't have
momentum like normal. Upon Taking
of from a red light. I knew something
was not right. Drove slowly till I could
find a spot to park it. Once my husband
had a look underneath there was
steam hissing out of a small hole in the
Flange Gasket in the front of the
exhaust we're it goes up to the engine.
We thought it would be a easy fix.
While taking the two bolts out one
broke off & what was weird was it was
welded. To make a long story short he
bipassed & cut that area off & used
straight pipe ect. Got it back on there
no more hissing thought problem was
solved. As he went to test drive it he
heard a Grinding noise coming from
somewhere as the RPMs went up, it
shifted gear & stopped.. Right now we
have been racking our brains trying to
think positive & hope nothing went into
the engine from the exhaust. Please
help.