Could be a newer flash. We were discussing this in another thread recently. Does it do it at idle sitting in park while warming up? My truck never did this until the latest flash was installed either. The reason is to exercise the vanes in the turbo so they don't stick. This in turn will reduce the need to tear down the turbo for cleaning due to sticking vanes. In theory it should also reduce the chance for any over boost or under boost conditions due to sticking turbo vanes. You should still be running cetane boost regularly. I run Diesel Kleen at every fill up, but a lot of guys like the Ford stuff.

 

Thanks!