everything was finally good (except for the odd rattle...) w/my DSM for the past few months and now the car's acting up again

I notice that whenever I cruise above 70mph, the O2 sensor will go dead (hold at 0.15V or so) and the car would buck/misfire. Pulled the CELs and they were:
p0300 - random misfire detected
p0136 - o2 sensor circuit malfunction (Bank 1 sensor 2)
p0141 - O2 sensor heater circuit malfunction (bank 1, sensor 2)
p1105 - fuel pressure solenoid malfunction
p1400 - manifold differential pressure sensor circuit malfunction (this I always have since the Evo III intake doesn't have a bung for the MDP lol)

Is it just the O2 sensor or something worse?

Also, does anyone on the west side (by 10 and 405) have a logger/OBDII reader? think I lost my Palm's charging dock

Running an Evo III motor (1g CAS) w/Evo III B16g and supporting mods

Low voltage means it's detecting lean mixture if it's functioning. A wideband would tell you exactly what's going on but when o2 sensors die, it'll cause your car to run rich since it's now flying blind. Check for boost leaks and what's telling you o2 voltage? Afc?

sounds like random misfire caused by running the 1G CAS. I had that same problem, and I never had the issue for about a year of running a 6bolt engine with a 1G CAS, then all of a sudden it started doing it. If you put the car in neutral and let it drop to and idle, then put it back in gear and keep driving its back to normal for a bit?

CAS/ ECU/ certain parameters are met and the ECU starts looking for misfires. And the ECu has no real way of telling if it misfired other than a variance in speed from the CAS sensor. And the 1G CAS's aren't as accurate at the 2G ones, and the ECU sees the variance and freaks out. DSMlink can disable the ecu misfire check, or 98~99 ecus can be flashed to disable the misfire check