Pseudorotation corresponds to the low-barrier change of ring conformations of similar energy, which can be treated as a kind of vibrational motion or similar to 1DHR. For THF, character and energetic order of conformations has been discussed for decades and results are very sensitive to the level of theory. This makes this system a good test case for the MuFi method to demonstrate the effect of poor LoFi data because one can be confident that a low-fidelity method computes the THF pseudorotation PES shape fundamentally wrong. We use the qualitative data by Rayón and Sordo 32 computed at different levels of theory (MP2 with three different basis sets: cc-pvdz, cc-pvtz, and aug-cc-pvtz). Fig. shows the LoFi data from the cc-pvdz basis set and the HiFi data from the aug-cc-pvtz basis set.