RPM jumping 95 E320
 

Help, my 95 E320 went into an indy shop with a missing problem and slight surge in rpm at idle.. Missing problem has been fixed with the installation of a new harness coilpaks, spark plug wires and sparkplugs. It is still jumping at idle. mechanic says still need mucho bucks and not exactly sure what is wrong. I have read in the forum that there may be a vacumn leak between the brake booster and intake manifold and would like to know if anyone has seen this before and knows the place to look. If I remeber correctly I first noticed this when I was at a stop light. Foot on brake and idle started to jump.
Any ideas would be sincerely appreciated..
Thank YOu