What year of car? Swap?


Code 3 is Map Sensor(defective circuit, or unplugged, defective sensor)

Code 6 is ECT Sensor

Code 17 is VSS Vehicle speed Sensor.

Code 41 is Primary Oxygen Sensor - Heater
circuit malfunction

The O2 sensor and the MAP sensor would explain the startup issues. But why wouyld you say a gasket leak? If your cel is on then fix those problems first.