Premium Member 2001 SLK200K/2001 SLK320
It's not that easy (of course it isn't) .. the Ignition Switch is secured by 3 screws which are an absolute PITA to get to, yet another job that involves middle-aged men getting into positions that they shouldn't really be getting into 🙃I surely missed ignition switch test. I’ll go back and review your advice.
Key in run position always has noise from throttle body area but can’t remember if fuel pressure regulator always does or it was after relay contact. At work now, so another 10 hours before I’m under the hood again for update.
Spare ignition in the column has a 10mm bolt with a clamp that i loosened, but appears there is another form of attachment holding it in the column. Looks like an easy plug/swap if it wasn’t still in the column.
As @Dave2302 has just said, pull the harness plug and test the wires first