Sub is hard to start when cold, takes 5-8 seconds of cranking to start. New plugs, cap, rotor, gas filter & wires. Only searches on internet I could find suggested fuel injectors are dirty. Anyone have history with this problem. Mileage 75,000, 4x4. Thanx in advance, Bill.

Most likely your fuel pump getting weak. After it sits the system looses prime & pump being weak takes longer to get up fuel pressure to start. These are very common problems on those late 90's Vortec motors. They are trying to push so much pressure they just don't last long.