over the years, chrysler, dodge, plymouth and now jeep had little holes drilled on the lower part of the muffler to drain the water byproduct of combustion. fuels which are carbon compounds are burned inside to the engine combining 21 % of the air produce H20 (water), NOx, CO, CO2, O2 and unburnt fuel HC flowing through the exhaust system. all of them are in gaseous form except for water which collect at the bottom inside of the muffler. now, other manufacturers are following suit for the same reason of extending the service life of the muffler. if you don't have a weep hole on the resonator of the muffler, water sits and constantly react with steel. remember, rust never sleeps. if you drill holes, don't be surprised to notice water dripping. the size of the hole can be as small as 1/8 of an inch (could be smaller) without any change in the sound or silence of the tailpipe with the engine running.