Wish that the past and good/bad futures were "Time Attackable" in some way? As in no 1-up boxes or Future/Past Signs? I've found out a neat way to get the Past/GoodF/BadF levels into "Time Attack mode." First, you need to put this in the file sonic.ini(run "sonic.ini" to get to the file).
You also have to get the patch, but you might know where that is already. It will have the Debugger thing in the sonic.ini file already, but there will be some crap near the bottem that prevents the debugger from working. Just make sure User=Debugger is the only thing below [Secret].
Now, run Sonic CD, and then you'll notice that "Stage" and "FUNC" are now in the Toolbar thing.
NOTE: you may want to do this on a new file, so start a new game, then when you are at PP1, go to "Stage" click R8, then 3, then either C(GOOD) or D(BAD). Beat MM3 for the ending. Now all levels will be unlocked for Time Attack on the new file.
Now go to Time Attack, then, say we want to "Time Attack" Palmtree Panic 1 Past. Select any level you want(Palmtree Panic 1 is recommened if you want the PP1 Past time to be recorded, lets say the file your using is your "Past" file). Now, when you reach PP1, go to "Stage", pick R1, then 1, then B(A=Present, B=Past, C=Good Future, D=Bad Future). You'll now be in Palmtree Panic 1 Past, but there will be no Time Posts or 1-up boxes! This can be done on any level, and you can select any level in the time attack menu to get stuff started. When you beat the act, the time that you made will be recorded onto the level that you went via time attack screen.
Also note that when in the Good Future, the Bad Future music will play(For some reason though, at SS3 Good F, when you start racing Metal, the GF music will play).
This means with this trick, we can open Submissions for EVERY level in the game! And some tricks for the Present levels won't work for the other Time Zones, so this means theres over then 24 more levels to time attack!