Odd scorching near injector tip?

[96F2507.3]

Hey, folks - does anyone know what causes the injector to become scorched near the tip? It's the only one that came out looking like this, and the injector cup is similarly scorched. No coolant leakage, no coolant in oil, nothing.

Thanks, Lynn

[Evanla_33]

Looks like blow by, maybe that copper washer is in backwards!