You have multiple symptoms that may or may not be related, only diagnostics will determine if that is true.
Until you repair the CEL or gain access to a scanner and determine that the scanner will communicate and there are or are not any fault codes present we will go with the assumption that there are no fault codes stored.
Just an FYI...
IMO you should have diagnosed the "over charging", "not charging" issue before installing an external regulator in case the issues are related.
If that is true that they are related all you did was cover up a symptom, you did not properly repair an issue.
Here is Chryslers Diagnostic Sequence for Driveabilty Without Fault Codes or Codes 51/52.
Not all apply, however, with a Spiking Tach/Speedo, Charging Issues, Stalling and Misfire I would run tests NF-2A, NF-3A, NF-4A, NF-5A, NF-9A
NF-2A)CHECKING IGNITION SYSTEM
Use an Adjustable Spark Tester to verify the system is capable of a minimum of 25 KV at all 4 cylinders.
ADJUSTABLE SPARK TESTER
NF-3A)CHECKING FUEL PRESSURE
NF-4A)CHECKING COOLANT AND TPS CALIBRATION
Backprobe the Signal (OR/DB) and Signal Return (BK/LB) Lines at the TPS connector and read the voltage, closed throttle .30 - .90, slowly sweep the throttle open watching for voltage spikes or dropoffs, WOT should read above 3.50 volts.
Backprobe the CTS connector and read the voltage, voltage translates to an exact temperature.
NF-5A)MAP SENSOR CALIBRATION
NF-9A)ENGINE CONTROLLER GROUNDS
Disconnect the SBEC connector and check each controller ground circuit for continuity to ground.
Continuity should read under 5 ohms.
Controller Grounds are...
SMEC 14 Pin Connector
Cavities 2, 6, 7
SMEC 60 Pin Connector
Cavities 5, 15, 16,
Cavity 4 is the Sensor Ground and grounds internally to Cavity #5.