So many truck come into our shop with high EGT's, turbo lag, excessive smoke output, and bad fuel mileage which are all symptoms of a boost leak. It is so common to devlop boost leak that we now require all trucks to have a boost test done prior to strapping them down on the dyno. What's funny, is that no one shows up knowing they had a boost leak. The reality is that even if you can hit peak boost, you may have a leak, especially if you have a variable vane turbo. Variable vane turbos will change vane position and other operations to try and achieve a desired boost number which may cover up a leak in the charged air system.