383 intake manifold change AFR big time

I run with Spectre Cold Air intake Spectre Performance Musclecar Cold Air Intakes 733 thats why I dont do the jettings when it's too cold and the height is no problem. Today it's about 35F here...

The way I use to tune a carb is that I'm finding an cruising (eco) area that works, then finding an Pwr area that works, then finding a jet/rod combination that matches that areas. Then I go for WOT afr settings and it use to work.
The reason I start this thread is that I was amazed that an intake manifold made that HUGE difference in afr and I'm not yet sure that it isn't a hidden vacuum leak that I cant find, the jetting is like a top performer 440 but as you can see it's a fairly mild 383...