Hi,

My 1991 Volvo 240 has a exhaust leak between the first and second muffler,
right where the first muffler attaches to the pipe that eventually goes to
the second muffler. I am assuming this leak relieves some back pressure in
the exhaust system. Could this leak (loss of back pressure) make the O2
sensor work improperly or have any other effect on my car. Like can it can
it cause a loss of MPG/Power due to improperly interpreted parameters the
computer system is recieving, or any other problems?

Thanks