Thanks for the tip on the MAF, I did clean it along with the other
things I did for a tune up (plugs, fuel and air filter, oil etc.).  The
low-load rattle is gone now but I am not sure which of the things I did
made it go away.

The plugs were clean and a good colour but the gap had widened from .054
to a range of .075 to .090.  I could believe that the extra wide gap
might have been causing the rattle as it would affect timing and quality
of ignition.  I think they are the original plugs and the truck has
130,000 Kms (80,000 miles) on the clock.  Fliters were a little dirty
but not too bad.  I'm interested to see if I get any improvement in
milage.

On the MAF tech tip site above, I was wondering why he didn't just clean
the MAF element by opening the air box.  When I changed air filters the
MAF was right out in the open and very easy to clean.  You would have to
follow his procedure if you wanted to take it right out but that should
not be necessary just to squirt some contact cleaner over the element.

Incidentally, I also did my rear brakes and changed oil.  I was quoted
$100 labour for the brakes and $160 just to change the plugs.  Brakes
took 20 minutes, and plugs about 45 minutes (pretty tight getting in
there).  Oil change is a 5 minute job.  Flat rate, book pricing is the
biggest scam going!

Stephen