Rang JBS the other day and asked whilst my car is in, if it was possible to do a boost leak test and he told me they advise against pressuring up the system as it can damage the seals in the turbo, so I asked how they perform a boost leak test and he said a road test

Now a few guys on here have had boost leaks test done so it got me wondering if there is any weight behind what he told me ?

Also 16804 does this mean my cat is actually dead, he said with pretty much certainty that it meant it was even though I have been getting this error for over a year and my car passed its last MOT "just" with the same cat, he reckons the cat will be doing nothing now ?