i know that egt are good monitor device for ingnition timing, will it also read temp between lean and rich conditions? Since i know that lean will produce hot exhaust temps. so will egt do both?

 

Technically, yes. but accuratly afr ? i dont know about that.
I never used one as I cannot afford one.
if i understand the question, then you are asking if the egt can tell you if you have correct afr and that answer is no. thats why they made 2 seperate gauge.
can some one give the guy a better answer before i say more stupid things?

 

there was an informative EGT thread a few days ago. search.