Headers glow, it's not a problem. I should take a pic of mine after a long high RPM run... glows cherry red and I'm running too rich.
As for running lean, an engine running hot is not even a definitive indication. What do the spark plugs look like?
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-Harry
AIM: NDcissive
CRX and Pre '92 Civic, Engine Tech and Tuning, & Track and Autocross Forum Mod