Power difference Tacx App vs Epix 2nd gen

#1: Do you make manual zero offset calibration on the 4iiii via Epix before EVERY ride? If not, DO. #2: i suppose you have a single-sided 4iiii, which meausere only the left leg and multiple it with 2, if the #1 is good, then probably your left leg is so weaker than your right leg, apprx 45-55% balance  , in this case the single-sided bike powermeter is always reading lower than a total/dual sided powermeter. the Neo is a "total", and a bit always lower than the accurare total/dual powermeter on the crankset (so if the Neo 148w, usually on the pedal/crank it is 149-151w or a tiny bit higher, depending on many factors). Probably you are sitting too high on your bike, usually the people has leg imbalance when they sit too high, check pls the following: if you are sitting on the bike with bibshort and bike shoe, with unclipped , put your both heels to the pedal, and try to pedal backward with contiously touched with both heels the pedals, if you can pedal without hip movement, so your hip is rock steady, no wobbling left and right to get closer to the pedal , then your saddle high is good. if you cant do it, it is too high.