I have a 98 big block suburban. Truck starts and runs great when it’s cold but after I drive it and let it sit for 20 plus minutes she hesitates to start. Long crank time then when it fires it stumbles a little and smells like raw fuel. After it clears out it will have a slight stumble sitting at a light. There is no check engine light on. From what I can gather seems to be injector issues but some are saying fuel pump check valve. What are peoples thoughts?