All the factory service manual says about the panel is that it was put there for improved aerodynamics. Nothing about any other functions. I'm thinking about taking mine off permanently at the next oilchanges. Perhaps it will facilitate better cooling when its off. The M103's run pretty hot in the 300E's, even more so compared to the M119' s in the 400E's. At least mine does.
F.J.

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F.J.
81 300 SD grey/palomino 168K miles
84 190E 2.3 black/grey 64K miles (wrecked)
85 190E 2.3 maroon/palomino 92K miles
88 300E desert red/palomino 204k miles
(made to look like a '94-95)
92 400E desert taupe/creme beige 120K miles
(converted to 94-95 E420 looks)