This is up my alley. Been there.
Had the same problem on a 3.8L.. Turned out to be the CRANKSHAFT POSITION sensor. Comes up with those same codes for some reason and I also swapped the camshaft sensor with no help.. Hard to troubleshoot. Eventually for me it got more violent and sometimes engine stoped at bad times. It still could be wires to that area from the Ignition Module but my $ is on the sensor.
Buick Lesabre, Park Avenues have same problem . same engine.
Requires a puller for the harmonic balancer and a good impact wrench.. actually its not a balancer but a wheel on this engine.
Good luck..
