need to remove fan cover insullation ?

[36brua]

So I've been working through the stickey engine bay thread (wow stuff) trying to see how many people are removing the insulation from the fire wall /heater fan box cover for clearance, but can't really tell.

I have read about just cleaning off vertical face of the fan cover only (RM European). Is this necessary or just to free up a bit more clearance at rear of engine? I plan on installing the M3 covers eventually.
input ?
Thanks

[748Snowman]

I'm removing it off of mine, basically looking for rust, but I don't really plan to replace it. May just use a under coating of sorts on it.