lets say a PS 9 decoys or swarms up another pilot who has Veteran Instincts. Does VI add the 2 PS. or does the effect of Rorak, or swarm supersede VI.

I feel like the new effect overshadows the old effect, but an interesting thought i had.

The Swarm Tactics overrules the VI as it's the latest pilot alteration.

From page 4 of the FAQ:

Altered Pilot Skill

Some abilities alter the pilot skill value of a ship. If several game effects alter the pilot skill of a ship, only the most recent effect is applied. For example, if a Green Squadron Pilot equips Veteran Instincts, it increases its pilot skill from 3 to 5. However, if it later receives the Damaged Cockpit damage card faceup, its pilot skill is reduced from 5 to 0 (rather than 2). Next round, however, Wedge Antilles can use Swarm Tactics to raise its pilot skill to 9.

right on. thats what i thought, but i figured i would ask

No problem. The only dumb question is the one you don't ask.

VI would still boost your PS if decoy was used, however that boost would apply to the ship with decoy now as your PS are exchanged

I think you have this worked out already, but here's an example. Consider Mauler Mithel with Decoy (PS7) and a Black Squadron Pilot with VI (PS6). If Mauler uses Decoy on the BSP, Mauler will shoot at 6 and BSP will shoot at 7. The VI doesn't just go away. As the FAQ explains, if Mauler used Swarm Tactics instead, both ships would fire at skill 7, and VI would be wasted that round.

Edit: tintip beat me to it.