Catalyst

Catalyst is the 16th mission in Los Santos, And the 16th overall.

Walkthrough
Again, this mission will work nicely, if CJ has some decent firepower beforehand.

At the start, there's the normal drive with Ryder again. After arriving at the train, CJ and Ryder discover that the GSF and Los Santos Vagos are fighting. CJ must then eliminate the Vagos gangsters, who are armed with Micro-SMGs. Ryder will also exit the car and help CJ, although his firepower isn't that formidable, so CJ will have to hold up.

After the Vagos are defeated, a Ballas vehicle will show up. The player should wait for them to leave before opening fire, as destroying the vehicle is not required, and this saves bullets. CJ climbs onto the train after the Ballas are defeated.

The train begins to move forward and CJ has only one minute to throw ten crates to Ryder, who is standing on the back of the truck with a GSF Member driving it. The player is advised to aim to the Picador's hood, so the crates may bounce to Ryder, or launch one directly at him. Ryder needs ten crates.

After getting enough Crates, CJ will enter the Picador, and gains a three-star Wanted level. He drives to the Pay 'n Spray near Idlewood to lose the heat, then drives the truck back to Ryder's house.

Trivia

 * The Ballas arrive in a Greenwood, which is a vehicle usually commandeered by the GSF.
 * The Freight Train is locked and unobtainable, and the driver cannot be killed.
 * Ryder will die if the truck was overturned.
 * CJ can throw crates high up in the air, which is, in reality, impossible.
 * If the mission fails due to time issues, the Picador will end up at Unity Station.
 * If all GSF Members die, the mission will progress as normal, indicating that Ryder has called backup that arrived off-screen.
 * The GSF member driving the Picador will disappear when the mission ends. However, killing him after stealing the crates will not fail the mission.
 * The explosive crates do not damage Ryder's Picador. However, it is not resistant to explosions.
 * Although the Picador has cargo loaded in it's rear compartment, it will disappear at the end of the mission. It cannot be saved.
 * This mission is a reference to how the CIA are smuggling guns to fund their international operations, only to end up losing some of their shipments to domestic gangs, which in turn accelerated the gang war.
 * Later, Mike Toreno makes a similar reference in Stowaway against the rival crew.