RE: Plugs, Wires & Coil Packs
I wouldn't touch the coil packs until one of them went bad. You could replace them at 150K, that would make sense but its not like they go bad at a specific mileage.
99' Silverado 5.3 4X4
Modified Predator 93 tune: TQM @ 40%, injector slope bumped up 4 levels,
125 MPH top speed, 5500 RPM limit,
TBS, 180 thermostat, 4" CAI with 9x6" element,
Bypass and De screen performed,
AVG: 16 MPG City, 20 MPG Highway