My 99 Silverado (226K) still has the original Evap Canister on it. It's running rough and a friend of mine suggested replacing it before I go spending money on coil packs. I was told the original on a 99 silverado has had leaking issues and that there has since been an improvment made in the design of the part. Does anyone know anything about this? Anyone? Plugs and wires were changed less than 50K ago and were checked recently. Any info would be appreciated. Thanks! Colleen in Wisconsin. GO PACK GO!!