Probably the two most important lines are the moulded ones going to & from the IAC module. When they split it's a BIG leak. And maybe the PCV line from the intake manifold to the valve cover. Otherwise just wiggle any line you can see with your fingers. Feel for broken plastic lines or split rubber connectors. No real need to replace functional lines. The white ones seem to get the most brittle with age.

Best of luck,

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Norm in NJ
Next oil change at 230,000miles