TH350 Vacuum line HELP

[bouncytruck]

HELPI rebuilt my TH350 at the end of last summer and it never shifted into 3rd properly. Last night was the first time I've had a chance to really test it out (we had a baby in January). It appears to be shifting into third if I'm not giving it any gas. When I step on the gas it shifts down to 2nd and won't shift up again until I start coasting again. I think it might be a vacuum line issue. right now, the vacuum line to the tranny is going to a port in the Edelbrock Performer intake manifold - the same one as the power brake vacuum. I switched it there because someone told me that is where it should be hooked up. Before the rebuild, it was attached to the carb (quadrajet). Where should the vacuum lines all be hooked up? I don't have a vacuum gauge. I really want to drive my truck again before the weather turns to rain