The benefit from disconnecting them in hot weather climates is the throttle bodies aren't heated up by the coolant (thereby heating up the intake air) when the car is hot.
No need to cap them unless you're worried about some small bugs/critters taking up nest in the tubes. If you drive the car enough you won't have that problem.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |