dejanat

Need some guidance here. I installed a Pat G cam and LS3 Top Half on my LS2. At the same time or shortly there after I installed complete Z06 dual mode Exhaust. I ran a vac line from the back end of the intake to the mufflers. Well while the setup works great, at idle with vehicle in gear the vacuum drops to 9 in Hg and butterfly valves rattle uncontrollably.

I did a vacuum test using mighty vac setup and found out that 12 in Hg is the minimum vacuum I need to keep the valves closed without rattling. 10-11 there is noticeable rattle, at 9 it is unbearable.

I have 12 in Hg at idle in park however as soon as I put the car in gear I drop down to 9 in Hg and the rattle is on instantly.

Any recommendations on how to fix this problem economically? I want to retain the functionality of the vacuum operated valves but want to get rid of the rattle at idle in gear. I only have a problem at idle in gear (A6 Trans).