GMC Repair: 4.8 misfire under load, crankshaft position sensor, crank sensor

Question
I have a 2000 silverado 1500 with a 4.8,when pulling it will
start skipping ,going along at highway speed 65mph it runs ok,if you hold it to floor it will skip,buck and puck out exhaust.engine code p0366 crankshaft position sensor performance.had misfires on 4 diff. cyl,no 3 worst. if you pull wire off no 3 plug and put a spark plug in it to watch the spark and load up engine the spark would go away at 2200 rpm.i swaped coils and wire no diff.i unpluged ecm and removed crank sensor and hocked pu multi meter and did pull test on wires meter did'nt move,changed crank sensor, fuel pressure good even under load.when i first started doing test and loading it up it would puck through intake now itif you give it a big free rev it will puck through exhaust.
hope you can help
Mark

Answer
Hi
I would check 2 things at this point.
I would check the crankshaft position reluctor ring mounted on the crankshaft.
I would then check engine mechanical, worn cam, collapsed lifters etc...
Here are other possible causes of p0336
The following problems may cause this DTC to set:

Poor connections and terminal tension at the sensor
Crankshaft reluctor wheel damage or improper installation
The sensor coming in contact with the reluctor wheel
The engine running out of fuel
If the crankshaft rotates backwards, this DTC sets. This condition is only with vehicles equipped with a manual transmission. This condition can occur when a vehicle is on an incline and the clutch is released and an engine stall occurs.
I would also think, if you believe it is more electrical than mechanical, consider the PCM being at fault.
I hope this helps.
Follow post back, if needed.
Good Luck
Pawl