The challenge is difficult because more often than not you die from the launch, you need to spend a long time setting up the grenade pile, you need sputnik and black eye skulls, and catch skull makes gathering nades easier.

Also it is called the warthog tunnel because in the game's code there is the code of a warthog and we found out that the code is inside the tunnel, so we named it the Warthog Tunnel. The warthog has been found by drbizz before this challenge was complete.