This was a home with a side vent that ran a few feet from the dryer, so we knew there was an issue when we saw the decreased air velocity.  We were able to clean the lint from the vent, but it did not increase the air velocity.  The accordion style foil transition vent was installed in such a manner that created a kink behind the dryer, and this created an obstruction of air flow.  Once we changed the transition vent to a DryerFlex, the air flow was restored and the dryer was once again, good to go!