Text Tutorial :
1. Call Pegasus
2. Press X then immediately after spam O
3. Check if you did the glitch right by calling Pegasus and they should say your vehicle has been delivered (the vehicle shouldn't appear in your map}
4. After you confirm go look at the spawn locations Pegasus Vehicles typically spawn at.
Spawn Locations ( Taken From Reddit User Nolms ) :
1. You only need to do this glitch once after that just get close to a spawn point and your chosen vehicle will "always" spawn at that spawn points.
2. Make sure nobody is close to the spawn points.
3. If you are duplicating only using one spawn point keep an eye on your dupes or they will despawn.
4. To get out of the glitch log off and sign back in