No, you cannot. If you purchase illegal gaming enhancements (cheats), such as extra Flezz or forum visits, you will be disqualified from the competitive aspects of Forumwarz.
The competitive aspects include Domination, Leaderboards and Kyoubai.
This is to keep the game fair for other players who did not purchase cheats.
However, if you have purchased alts, you may enter your non-cheating alts into any of the competitive aspects of Forumwarz. Note that cheats are not applied account-wide, but to individual characters.
You may purchase an un-cheat option if you later decide that you would like to participate in competitive aspects. However, this will cause you to lose many items.