Emissions Issue 2011 Malibu

Hello,

I have a 2011 Chevy Malibu 2.4 Flex Fuel roughly 80k miles. I have been
having a pesky emissions code P0442 come up for the past six months. I am
noticing the smell of gas when started from cold. The car doesn't feel like it
has full power when accelerating onto the highway. And I noticed the gas
mileage has dropped significantly.

I have changed the canister purge valve twice, the Mass air flow sensor, the
gas cap, and the upstream O2 sensor. Any ideas as to what this could be. It
is the only code that comes up twice when I run a diagnostics test. I have
taken it into a mechanic and they were unable to help. Any help would be
greatly appreciated !!