Don't know what the GM part number is but PPE makes a silicon version that is much better (described at PPE Performance Silicone EGR to Cab Coolant Hose 04.5-07 GM 6.6L Duramax). However, the source of the leak could be the plastic connector between the hose and the firewall so, while you're at it, replace that connector with the stainless steel PPE version shown at PPE Stainless Steel Heater Hose Connector 99-14 GM 6.5L / 6.6L Duramax. You'll need a fuel line disconnect adapter to remove the plastic connector from the firewall inlet.