When you got the new MC did it come with a new gasket that goes between the booster and the MC? If it didn't did you remember to pull the old one off and install it on the pushrod?
I did that once. My brakes were worse, and my idle would go up when I pushed the brake. It took me about half an hour to figure out what the hell was going on!
1994 C 280 117.5k, White (Good as new)
1997 Toyota Camry 149k Miles (Not so pretty anymore)
1990 190e 2.6 95k (Sold-Should not have)
1981 240d Stick ??? Miles...sold