I'm trying to make the 3dfx version of the game faster. It's running OK until I'm in the middle of firefight around buildings/big ships and shots fired. The games slows down a little bit. Not much, but it's visible.

Here's what I already done to make it faster:

1. According to another topic on gog forum, I switched my windows resolution to 1280x960, I amended it also to that resolution in the dosbox configuration and the nglide configuration utility.
2. I turned the vsync off in my Nvidia setup (I turned off all advanced gfx options for that game)
3. I tried to switch dosbox core to 'dynamic' (it didn't help very much)

How can I get the game a little bit faster?
Are there any more tweaks I can make?

I don't know, perhaps a faster cpu will help, but it's very well possible the game activates frameskipping during firefights.
Or you can get an old Pentium with a voodoo card, though resolution will be 640x480.

The bad 3dfx performance was enough for me to convince me to play the software version instead which is much smoother in dosbox.

I turned off vsynch from within the game and set resolution to 1024x768 - that fixed it for me.