Good work, guys; the oil filter relocation kit may be a factor.
Unfortunately the MM3 does not support a pressure sensor input, just the EGT probe.
From what I have read, the stock oil pressure sensor is simply a switch, on/off for low-pressure warning.
If you have the factory oil pressure gage it uses a calculated value generated by the PCM.
If you want to see the actual oil pressure you could thread a pressure sender or hard line at the 1/8” NPT port on top of the oil filter housing and install a gauge inside the cab.