Here's the latest update of my test quest: http://www.freewebs.com/masterpikachu/ZC%20Content/Incomplete%20Quests/LOZ%2DGeneration4.qst
I made an L4 Leever that moves at the same speed as the L3 Leever (300), uses the L2 Leever movement pattern, and has a misc 3 (speed when emerging) of 4. But it's quite a bit buggy! It goes through solid combos, only to get stuck on them. It also goes through the edge of the screen, which enemies can't pass through, and it causes the custom leever to leave the screen at the top and bottom, and appear on the opposite side when they leave through the left or the right.
EDIT: I tried changing the speed to 200, and it didn't go through the edge of the screen, or any solid combos when it first emerged, but the second time it emerged, it went straight through all the solid combos, left the screen on all four sides, and mysteriously disappeared! So then I reset the speed again to 100, and it worked properly. I just realized that it's a bit buggy when its speed is higher than 100 or so.
EDIT2: The bug that happened when the speed was set to 200 only occurred when the emerging speed (misc 3) was set to 4 (or possibly anything lower than 17). It worked properly at a speed of 200 when I reset Misc 3 to 17. However, the bugs that occur at a speed of 300 still happen even with a misc 3 of 17.
NOTE: My test quest has no password, so feel free to edit the L4 Leever that I put in there, and change its speed and its misc 3. If you see any more bugs besides those I have mentioned, let me know.