Several questions!

I have several questions that you might have researched or have come across.

Both front sun visors don’t have mirror covers on my 2004 LS.
Is this standard for this model? I would like to replace them with the
ones that do, but the dealer needs to have something to go on like a VIN , model/package or a part number of the visor.

What's the RPM / tachometer marks for Yellow and Red for the
Vortec 4200 L6 (4.2L )

Has anyone been declined a factory warranty claim for any reason, due to rust proofing and/or undercoating?

The heating system seems only affective only when the blower is used. I only have a basic model with out all the auto environment controls.
Is this normal?

I also have a 2004 LS and I don't have covers for my sunvisor mirrors. Wish it had the same visors as my Sonoma SLS that are lighted, covered, and have a second smaller visor. You could try ebay or look at gmpartsdirect.com to pick them up. I am thinking of this mod, but am not sure if the wire harness is up in the headliner for the lights to work.

As for rust proofing and/or undercoating, if you have not done it, I would not bother with this as I think it's really a ploy for the dealer to get more money.

With the heating of the system, I would assume the blower has to be switched on instead of the fan speed set to "off" to circulate the air into the cabin. I have found that if you turn the temp set all the way to red, it gets real hot, then set it lower once the desired temperature is set so you feel comfortable.

I believe the redine is 6,000 on the 4.2 but the computer will not let you rev too high anyway, thats why there is no yellow or red markings on the tach.

Joe,

So far (as far as I know) my concern is not having much heat output unless the fan speed switch is set above "1", even with both driver and passenger temp settings....all the way up. Most other / older vehicles that I have driven allways had good heat output at highway speed with or without the fan turned on.