If i want a better chance of scanning an uncommon or rare NPC does it help if I boost my ship with scan items before I clear an NPC slot?

No. Increased scan only determines which NPCs you CAN see, not which ones you WILL see. Some NPC have a cloak value and to be able to see them you need at least that much scan. Which NPCs, of the ones you are able to see, show up is determined by the RNG.

If I understand you correctly, it should my odds of scanning a better NPC then, since I would have the ability to scan ones I could not never see before. It works for me in PVP, with higher scan i see different ships. problem with NPC's is you need to clear them of your board before you can rescan.

If I understand you correctly, it should *boost* my odds of scanning a better NPC then

Sorta.... If boosting your scan through additional mods or with buffs puts your scan over the cloak threshold for a particular NPC, then it will be added to the list of POTENTIAL draws. If something (say a Rogue Labpod or whatever) is already available due to your scan score, raising your scan further does NOT increase the chance of finding one.

got it. thanks for the explination