Low power and intermittently no start

[Chamberpains]

The 1st code looks like a exhaust back pressure sensor reading incorrectly. Possibly plugged with soot. Start with checking the sensor and wiring. Then check the sensor housing feed tube is free and clear of soot. You can often use pipe cleaners to clear out the tube.

2nd code looks like

Fault Code 2272: EGR Valve Position Circuit – Shortened to Low Source or Less Than Normal Voltage

Code Types
FAULT CODE 2272 PID 27 FMI 4 (SPN 27 FMI 4)

EGR valve position circuit shorted to low source or has less than normal voltage. ECM suspects low Signal voltage at EGR valve position sensor circuit.

Both of those codes will cause the problem you describe.