340 idles at 1500 won't stay running in gear

replaced the needle and seat last night, no big difference. i did however get some carb cleaner and made another run at the intake manifold. this time i sprayed enough to make a puddle in one spot and heard it level out. so i have a vacuum leak one the drivers side i/m right in the middle. checked the bolts again and they are nice and tight.

which leads me to my next question, is there one recommend gasket or way of doing it, I've never had to do one before.

appreciate all the help guys, I'm still learning as I go with this car and this site has helped a lot.