tunnel ram issues

ok went out to the garage used a temp gun this time and checked bank 1 of the engine front two where 240ish and rear two where five hundred after like two minutes of running so I called my engine builder and we where talking and he said sounds to me like u have a vacuum leak and leaning out that rear four cylinders he said try turning out the idle screws on the rear carb till the temp start going done and I did that it helped some still high so got the old brake clean can out and started to spray sure enough I spray the rear area by the carb and the idle changes so its ether my carb gasket the carb adapter gasket or my vacuum port where I draw for my brake booster. im thinking its the vacuum port I will do some more testing tomorrow and will update #-o