Okay, I've decided to leave the end of level 2 alone for now and move on to looking at level 3. Not many tricks here. Once again I'll use RoyHess's run as a base and list improvements since this is the simplest way to describe a route.
Here's RoyHess's run:
http://www.youtube.com/watch?v=mABmaZpSyDc
The first and biggest possible improvement to his run is right at the start; instead of dropping into the pipe you start on, taking the elevator down at the end of it, then running and force jumping up to the big square elevator elevator at 0:15, it's a full 10 seconds faster to drop off the starting pipe into the pipe below, then run out of the other end of that pipe and jump across to the elevator. You can even do this without taking fall damage - it depends on where you land.
A well-aimed rail shot at 0:20 can blast the enemy trooper out of the way and save a second.
With better luck and execution, you can get back through the big door before it closes to skip having to open it again at 0:33.
The second-largest timesaver on this level is force-rail-jumping up to the top of the elevator at 0:44 without waiting around for it to start moving.
I was kind of hoping to find a way to skip having to call the elevator down again at 0:38, but I don't think there is one. I tried leaving a projection on the edge of it in the hope that it would stick on the ceiling when the lift starts rising and block it, but it turns out lifts pass straight through projections. I guess you could get lucky with a force push and get an enemy there instead, but they would walk or slide off and even if they somehow didn't, they would die too quickly for it to be helpful.
It
is possible to wait (before going and cutting the wire) in the room with the two switches that call the lift and open the big door, and then press them both at once when the elevator reaches the top, run and cut the wire and make it back to the elevator just as it begins to rise. I'm fairly sure, however, that this works out slower than calling the elevator after you return from cutting the wire. Either way you have to wait around for the elevator to travel (all the way up if you call it before cutting the wire, and all the way down if you call it after). The tradeoff is just between the time you spend waiting in the control room for the elevator to
start rising if you decide to call it before cutting the wire, and the time you lose having to go into the room a second time to call the elevator if you call it after cutting the wire. Since I figure the first is a bigger length of time, I figure we should call the elevator after cutting the wire. (Of course, if for some reason we were to decide not to use the force-rail-jump up the elevator shaft, the balance changes and it'd be much faster to call the elevator before cutting the wire. I see not reason at this stage not to use that jump, though.)
When grabbing the red key, it would save a little time to also hit the switch to swap targets from the base to the asteroid. There's a delay after switching targets before you can fire the weapon, and you can see that RoyHess loses a couple of seconds at the end of his run because of this. Switching the targets on the first trip into the firing room means the delay won't hurt our time.
By the way, as well as the wire you can cut to permanantly open the door to the firing room, there's also a (quicker to access) switch in the room RoyHess is in at 0:25 which opens the door, but if you use that one then the door closes when you approach it (the plot idea behind this being that the imperials go and flip the switch back after you leave the room, I think). I was hoping to try and find a way to circumvent this, but failed. There are basically three approaches I looked at: avoid the trigger, hit the trigger but get through the door in time, or block the door. Avoiding the trigger isn't possible; it fills the entire height and width of the pipe. Getting through the door in time isn't possible either, even with diagonal running and 4 stars in speed and you dropping in through the hole in the roof of the pipe near the door. Finally, it's fairly easy to time closing the door so that a stormtrooper there gets caught under the door, but they get immediately pushed down into the slot in the floor that the door drops into and so the door isn't held high enough open for you to be able to fit underneath. Even if you could get through the door, unless you did it by bypassing the trigger to close it entirely, you'd probably just get permanently trapped in the firing room. I think this is another idea to give up on.
We can save some more time over RoyHess's run by skipping the unnecessary detour he takes for health and shields at 0:52.
If we need shields for level 4, we can always take a second to grab the Armor pickup behind the lift at 1:05.
After increasing the weapon to full power, I'm kind of torn on whether the fastest route back to the firing room is the one RoyHess uses, or to lower the forcefield, run into the pipe, forcejump out of the pipe, drop into the pipe below and enter the firing room. (RoyHess's route is much easier, though). Whoever does the level should time both possibilities.
I don't have any other thoughts on level 3. Will look at level 4 now.