When I changed MY water pump back some years ago, that begat a whole slew of things including a re-core of the radiator, powder coating some metal parts including fan shroud, fan, etc., changing all the hoses so affected and a few more items. I dropped everything below after lifting the front up very high. Based on recommendations from member Dave Gallon I believe I used a Laso water pump, and upon recommendation from Joe Alexander, bought a water pump gasket from Mercedes.
Now the Laso pump CAME with a water pump gasket. The OEM gasket from MB was something like $5 at the time. Wow, what a difference. The Laso gasket was like thin, cheap paper. The OEM gasket robust and substantial. No comparison. The only thing they had in common was shape.
Bottom line, don't use the gasket that comes with an aftermarket pump.