I have a 85 c4 with a 350 crate "replacement" l98 motor, have about 20k on it and was running great now suddenly I have code I cant seem to shake.

code 54, already replaced relay and still it persisted.

code 53:Low System voltage low, but I have no idea really what that is.

code 52, from what I've been told that's the fuel calibration, but have no idea how to change that.

Replace, ECM (3 times for other issues), fuel pump, fuel relay, tps. After the motor was put in I had it tuned at Hitech Motorsports here in MN, and it ran amazing up until now, just lookin to get a few months of enjoyment out of it before the outrageous snow comes back. Any help would wonderful thanks everyone!