I am going to elaborate about the background a bit.
The group has started with Escape from Mos Shuuta and Long Arm of the Hutt. After some time off the planet, they have returned to Tatooine. During one of the recent adventures, they found an abandoned research facility with a partly stripped Gozanti Cruiser. As one part of refurbishing this ship, they need a suitable Hyperspace Engine. They spent the last few weeks on/near Rodia and have just arrived on Tatooine, to talk to some old contacts for help in refurbishing the Gozanti.
They were told that there is a Wookiee technician (which they already encountered and helped in the past in another location) at Mos Entha, who could potentially help them in getting access to the hyperdrive.
Before departing for Tatooine, the pilot PC asked whether there are any upcoming podraces on Tatooine. I expected that wants to see one and gamble. After I confirmed that there will be a minor race, he was excited and said “I will participate in this race, no matter the cost”.
Therefore, I changed some plans:
They still got the hint to look for the Wookiee near Mos Entha, which will also be the place where the podrace will take place. The Wookiee is basically the chief technician of a somewhat reputable racing stable. In order to allow my PC to participate in the race, the original pilot of the racing stable will be incapacitated some days before the race. As the stable currently has no other pilot available, they will allow the pilot to join the race with their podracer.
My idea was that the pilot is intimidated right before the race, so he has hardly any chance to opt out. Furthermore, I am quite certain, that he will not step back from participating in this race. As the group has just arrived on Tatooine, and they were actually lying low in the past, I would not trigger their Obligations in this scene. Furthermore, they have not been openly asking around for a black market contact, but have asked some of their contacts.
Therefore, they will not be the actual target of the sabotage of the race, this will be the racing stable.
What happens if they fail the investigation? In the worst case, the podracer will be in the first place and the pilot will not step down from winning the race. Therefore, in the last segment before the finish line, a bomb will explode, potentially shredding the racer with shrapnel. The pilot will have the chance of one or two rolls to mitigate the crash and take a lot of damage. And yes, there will be the chance of death in a pod race. The players know that this is an extremely dangerous “sport”. So failing the investigation will not lead to an immediate PC death, but it is absolutely possible for the pilot to die in this race.
To come to your questions about who/what/when/where and why:
Suspect:
A rival racing stable (stable B) wants to outdo / embarrass the racing stable (stable A) that the PC’s will support.
Motive: Winning the race. As stable A has the faster pod racer, one of the heads of the racing stable is taking somewhat desperate measures to guarantee the win by sabotaging the most dangerous competitor.
Means: Threat to not win the race, otherwise a bomb will make sure that the podracer will not reach the finish line
Opportunity: one of the heads of stable B. He has the money to hire some goons, but can still be easily dismissed/killed/exposed by the PCs without causing too much trouble.
Crime: Blackmail, sabotage, attempted murder… I am not quite sure what the final wording of the threat will be. But I think it will be quite clear, that there will be an explosive charge somewhere. The PCs will have enough time to make sure, that no charge is on the pilot’s podracer itself.
Why bother: They want the help of the Wookiee technician. They will not have the time to check everything before the race starts. I am quite certain, that they will place some bets on their pilot, which they cannot retract at the point where he will be blackmailed. And the pilot will not step down from participating in the race. So they will be invested in winning the race to get the support from the technician, to secure their wager and to save their pilot’s live.
Clues: that is actually the point where I am not sure how to handle it. They will have the description of the person conducting / delivering the blackmail. I like the idea, that the threat can also be delivered by some item, which can also act as a clue.
But as I said, this is the point where I am somewhat lost in my planning. Today I was working out the racing mechanics and the track’s layout based on a number of different approaches I found online.