If the vacuum check valve is bad... what can that manifest itself as ?

My 300D 2.5's brakes are nice and sport/firm/solid feeling. Stock except for stainless steel brake lines (only $85!)

My 190E's feel like ****.

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(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k