Thanks guys.... both approaches are doing essentially the same thing. The file D.J. mentions does the trick. It is the one referenced by the game.

By changing the file reference in descr_effects, I assume the game is just being told somewhere else to look and getting the effects from there. D.J.s way involves less changes, so thats the way I have gone!

I now have the superb flame thrower particle effect the Shifty pulled together working in BI just like it did in RTW. Hooray!