The Sept/Oct/Nov 1999 issue of our club newsletter had an article and picture about an air scoop that had been added to the side air inlet on the D.   I spoke to the Cummins Rep at the National Rally in Richmond, IN about this modification. He told me that Cummins recommended NOT to do it. The chance for forcing water into the air filter in heavy rain could do damage to the engine. I would recommend that you talk to Cummins yourself before making this modification. -- JB Vaughn