ISL not performing

Thanks for the follow up. It made sense that it was a fuel filter problem and glad it was that simple a fix. I use NAPA filters on my ISL so there has to be a defect or improperly installed problem. Did you see/find anything that might explain why you had a problem with the NAPA filters?
Last year I had a little worse power/fuel problem which changing the fuel filters and the lift pummp $$$ did not solve. Here is a link to that adventure and education for those with Cummins engines.