Just read the post 6, problem with Fomapan 200 was that they had to re formulate the film as some of the materials were no longer available, at one time it was discontiuned, but due tpopular demand the they re made it but with different formula due to loss of some materials, but the 100 and 400 emulsions remaind the same, I have never used the 100, only the 200 and 400, the 400 was never an IR film, and never intended to be, but had some extended red sensitivity, which I found showed especialy well in Rodinal developer, certainly you do not need an orange filter to get Orange filter look skys, so do not expect IR results with 400, you won't get it, but lovely cloudy skys with out any filters
Richard