You are supposed to measure the vacuum in bar ;-)

The vacuum at idle should be 0.35-0.4 bar vacuum, that is 10.3"-11.8" Hg. 13" Hg is a bit too high. You describe that the vacuum climbs up to 5" from 0, that is not good either.

I would suggest taking the VCV off the IP and clean it. After that, adjust the VCV until you get the desired vacuum level.

The problem is that you are missing the switchover valve, during coasting the vacuum should be full vacuum (approx. 22" Hg), that can influence the gear braking you are experiencing.