Vacuum leaking carb after rebuild!

[Nickelcharlie]

I had my carburetor rebuilt in my 86 GMC 2 months ago and it was running great until till I incurred a vacuum leak at the back of the carb. Bolts were loose and after tightening the bolts the leak stopped. The leak came back a second time so I retightened the bolts, once again it stopped. The third time I replaced the gasket. This solved the problem, I thought. Cold morning start and the truck goes to a fast idle. Checking for the leak it agains shows to be leaking around the passenger rear carb bolt. Bolts were tighten equally and are tight! I am going to contact the person that rebuilt the carb tomorrow but was hoping to hear from from someone that might have experienced this first hand so I can repair it this evening.

Any suggestions on how to stop this leak? Thanks for your help!