Spaceship movement help

Hey, I'm working on a spaceship game, and I need help with the movement. I've tried physics and the custom and even car. But all have their own problems.

What I need is the ship to have a maximum velocity, e.g. 100, so using it's engines, this would be the fastest it could go. But, external forces could make it go faster, e.g. up to 1000. Also, if the ship is already going faster than it's engines alone could make it go, then it won't pickup speed from the engines (but it could change direction.)

Also it should be said that the movement needs to be 360 degrees with an inertia, so no turning on a dime.

Not to sound p*ssy, but I'm not asking you to code my game. I've made an H.S.C.E. edition, (a Horribly Sloppy Code Edition... edition) and on my T5800 (2ghz Dual-Core) and with one ship it craps my framerate to 50ish. So I'm looking for some ideas (Or a plugin, hint-hint, wink-wink).

Also pixel-perfect collisions, are a high priority.

If I sound like I'm rambling, I'm sorry. Thanks for any ideas.

The Custom Movement behavior does all this.

Check the forum uploads section. I believe David made a few examples.

I think the one he did for the 360 controller would be a great start.

Thanks, I know of that example but it dosen't have a "Top Speed". I need my ship to have engines that will only go (50) but with external forces the ship could reach a maximum of (100)

I'm pulling out my hair over this and I can't figure it out.

with or without physics:

if speed < 50

add whatever engine acceleration speed

if speed>100

speed=100