After the LQ9 swap the vacuum was to low to run the brake booster. So, I added a pump kit. Everything started off good, for about a week. Then noticed pump was running about every minute or so. I checked the line for leaks and found very minimal. Blocking off the vacuum hose with a good vacuum gauge showed that the pump was pulling 26" hg, reset at about 18". Let is sit and pump does not come on and holds vacuum. Reconnect the hose to the booster and leak starts. Checked connector , hose, new booster gasket. Only thing I could come up with is that the booster internal seal leaking. Replaced Booster, it lasted about 3 days. Pulling too much vacuum ? If so how to regulate the vacuum source ? need something , Tried a 2nd switch, SSBC style, same issue.