What do you guys think should i got Dry or Wet Zex NOS? What are advantages or disadvantages?

All so wondering if anyone knows of a way to mount it on the exterior, b/c this local stop want to charge me $400 for a exterior installation, and $200 for an interior one. Only reason why I need and exterior one is because my local race track here on event days through tech inspection won't allow interior mounted NOS lines. Trying to save some money with DIY.