Best use for level 4 is Nepping.

Like everyone knows, it's quite hard to level up here since every time you have a level, dirty modifiers bundlify all your AAA games and evil witches start giving them out for free to steal all your hard earned CV. But while giving more gives you less, recent studies have clearly demonstrated that the opposite is also true. I had 9.8x levels for a while and every time it rose above 9.9x, the forces of evil started their work and it dropped back to 9.8x. Dismayed by this apparent impossibility of ever getting more CV I stopped making giveaways and what do you know, it went up to 9.9x right away. This gave me a little hope so I made another giveaway, but the moment it was marked received I dropped back to 9.8x. One possible solution that I came up with is to Nep some Nep-Neps. Time to test the theory with a little Nep-train(lvl4).