ok, say i wanna use Flare6.spr (the sprite used for the Phase Gate), and instead of showing multiplied flare6 sprites on the phasegate I just want 1. is there anyway to do it?

Afraid not. Particle effects are handled by the server - the only way to do it would be to edit ns.ps and host the game yourself.

you could, however, replace the 20-something frame teleport sprite with a single frame sprite to cut down on the inherit lag when viewing numerous additive particles rendered with the HL engine...

however, you'll end up with a bunch of "missing frame" console spam if you do what lotus says. It might be worth it though - I did it when I played NS on an ancient 400MHz comp, and it helped a little.