[glenncof]

I had the same problem with my 1997 Tahoe. Exactly the same. Sounds like a fire cracker. As I recall this started after 100K miles.

AFTER carefully thinking about it I concluded the white smoke must have come from combustion chamber. But how does it get out?

Also note: The sequential sequential fuel injection has documented problems with sticking. (I use techron as specified by GM for this.) This may be a contributing factor. The firecraker effect would usually go away after injector cleaning with Techron. I though it was the problem but could not understand the smoke coming from the hood. Then at about 130K it didn't fix it.

I concluded some ignition crossfire is occuring with the plug wires and causing ignition at a time when the intake valve is open. I assume the smoke is coming out from around the injector nozzle.A GM tech pointed to some possible arcing when he replaced fuel pump.

I have replaced the plug wires a few month ago and have not had a problem.
Yea, 133K miles on wires is enought. I suggest changing them at 100K when doing rotor/cap and plugs.