The simple answer is that you should not have a leak after they replaced the exhaust, end of story, they must make this right, the EVAP canister is a charcoal type filter that is part of the pollution control system.
Function description of EVAP canister system
Depending upon the air pressure and ambient
temperature, fuel vapor will form above the level of fuel in the tank.
The Evaporative Emissions system prevents these HC
emissions escaping to the atmosphere.
In limited quantities, fuel vapors pass through a gravity valve (which closes at an angle of 45 ) located at the highest point in the tank and through a pressure retention valve into the evaporative emissions (EVAP)
The EVAP canister stores these vapors like a sponge.
Wednesday, September 9th, 2009 AT 8:36 PM