REWARDS - Respect
Welcome to The Truth's weed farm, which he wants you to torch it all before the cops arrive. You have a total of 5 minutes and 30 seconds to destroy it all with a flamethrower. Run the flamethrower over some of the weed until you hear a beep noise, which is your signal for it being destroyed and also when you can move onto the next batch. If you run out of ammo, there is more near the barn. It is ideal to strafe down one whole line of weed, while keeping the flamethrower going; this should burn all of the weed in that line except for the end where you stop.
Once all of the weed is burnt, go and talk to The Truth. While this is happening, a police helicopter arrives and The Truth hands you a RPG to take it out. Aim at the chopper and fire to take it down. Once you do, The Truth has you drive him to San Fierro, to the garage you won in the race earlier with Catalina. The mission is complete once you reach the red marker.