Color-tune plug????

[Albert Ng <ang@copper.ucs.indiana.edu>]

Dear Audi fans,

First of all, sorry for asking a non-audi related question.

My father has an old Mercedes('79 230) in Hong Kong, and he is planning to 
do some tune up jobs for his car. Yesterday, I received my father's phone 
call, and he asked me to see if there is a spark plug which called "Color-tune 
plug" available in United States. He explained to me that this plug is 
mostly used for tune up jobs, and it's actually has no difference with a 
common spark plug except the cermaic part of the plug is, instead of, made 
with some kind of transparent material, likes glass. He said that the 
purpose for using this plug is for one to observe the combustion 
chamber's condition and color thru the plug, while the engine is running.
Therefore, from the observation of the combustion chamber's condition and 
color, you, then, can adjust the right fuel mixture ratio. 

I tried to look around for this somewhat color-tune plug this morning, 
but no luck with it, plus a bunch of laughing and teasing. :( 
Thus, my questions for today is:

Is there really has such thing as "color-tune plug" or a plug like I 
mentioned above?

Have anyone of you heard or experienced with this kind of plug?


BTW, my father's also asked me to look around for a CO2 meter. Is that 
expensive? Any information about this? I appreciate any 
inputs/suggestions. :)



Thank You
	Very Much



Albert Ng
'87 5kcst
'95 Subaru Legacy LS
Bloomington, Indiana.