It could be the fuel pump, but it could be many other things too. Spark, fuel delivery, air intake -- these are areas to check for concern. A hands on diagnostic test is needed to find out what is happening with your specific vehicle.
RepairPal Certified shops can diagnose and repair your 2005 GMC Savana 2500. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.