i put new RTV blue sealant on the gasket betwen UIM and LIM. it says drys in a hour fully cures in 24 hours. do i need to wait the full 24 hours before starting my car?

 

I don't particularly like RTV but that's not the question;
Yes, i would wait the full 24 hours so it fully cures before starting it.

 

Why would you do that? The gasket alone seals without RTV, which should never be used on intakes anyways. I've only ever used sealant as a means for sealing things that don't use gaskets (some oil and transmission pans), and holding gaskets in place when they'd otherwise fall off during installation. Even then I use permatex ultra black silicone.

A little RTV will squeeze out when you bolt it down, and when it dries there's now a booger hanging inside the intake manifold. Over time, that booger will break free. Not that it's likely to cause any damage, but you never know.