if you look right above the exhaust tips there is a vacuum line connecting to the muffler.
pull it off and stick a golf tee (or anything else that will work) into the vacuum line hide the line somewhere since you're not not using it.
the muffler will now always run in loud mode. you can reverse this by just plugging the line back in.
if you like the noise buy hate the tips then just polish them up or buy some new tips.
02 BMW X5 // 97 BMW 328iC // 89 325is w/ M50 swap // 06 Audi A3 w/ APR stage II