TFX2 is a proprietary modification of FX-2, and, as I recall, it has some special additives. I used it for the first time last year, with Kodak TMX, when I couldn't find anything else. The negatives looked pretty ugly - thin, flat, gray - but they printed well. The times for FX-2 seem to work, but I can't guarantee them. There is a data sheet for this developer on the Photographers' Formulary website, but it just recommends 10 - 14 minutes, in a general way.