you need to completely rebuild the carb correctly. this includes installing most if not all of the parts supplied in the kit. check trouble areas leaking well plugs, worn throttle shafts, stripped threads, binding linkage etc etc. you also need to setup the carb as it came from factory, setting float height is critical. i told you how correctly hook the needle clip yet you didnt fix it and ran it anyway? did you read the mercruiser bulletin i posted? cliff's book is not a "how to" rebuild step by step it discusses theory and how to modify the carb. there will be a sheet that was sent with your kit, you can look up your carb number and it will tell you the float height. if you spend a few hours reading or searching on this forum you will find most of the answers and methods that are needed to successfully rebuild & modify these carbs. there are also a ton of youtube videos on rebuilding as well.
as far as a vacuum leak from the carb did you check to see if the airhorn or main body was warped? over torquing the mounting bolts will cause warping. also i the idle tubes are in a blind hole, i am not too sure how you were able to see the wire sticking out of the other end. i push wire in until it bottoms, mark the wire then check the other side, if they go in the same distance there is a good chance they are not plugged.