I am definitely going through the same issue right now. I have an Elite Direto X and a SRAM Rival PM on my gravel bike. With TR and my indoor trainer, my FTP is 233… but I have done 2-3 rides (about 2 hours long each) with my Rival PM and have had an IF (based on indoor power) of over 100 every time.
I have zeroed both PMs but still have a large discrepancy. No idea how to adjust for it, and it sure makes it hard to set a pacing plan for race day 