2003 GMC Sonoma SLS 4.3l V6, So I recently replaced the spark plugs and wires for new NGK ones, off of RockAuto. Those went smooth, then a new cap, rotor, and distributor all together from RockAuto, brand SKP. Everything went smooth until last night i fired up the truck and started driving it, and it felt like it was jittering, almost as if I was getting a heavy misfire while driving, but it was bogging down as well. Losing power, and the rpm gauge was jumping around. I later scanned the car and found a P0016 code. Now with the distributor new, and everything else new, the only thing I can think of is a shitty, already worn-down distributor gear, or the crank position sensor being finally worn down and shooting itself dead. Not sure what to throw at it yet, as I feel like it can't be timing chain issues because the truck was running fine for weeks before I swapped out this distributor and other parts. Any help is appreciated on what I should do next. Possibly might replace the crank position sensor, and maybe swap back over the old distributor, but aside from that, I'm stumped.

With a P0016 code in combination with the RPM gauge being erratic leads me to think the problem is the quality of the camshaft reference signal being produced in the distributor.

it surges down once and a while, while feeling like it is havinga misfire at idle, but doesnt go crazy, when i rev it to about 2k, it drops back down to 500 then goes down to 300, then back up to 500, so im possibly thinking just a bad distributor all together since it is aftermarket and the oem one never had any issues of such. only reason why I replaced it was because the ear was cracked when replacing the cap and rotor, and I didnt want an intermennent misfire.

I think that I agree with you. I would also confirm the spark plug wires are installed correctly and the distributor is clocked correctly.

Assuming you are certain that the wires are in the right order, it might also be a good idea to replace the crank position sensor with a quality unit if the current one is old. Maybe do that before messing with the new distributor etc.

How many miles are on this car?

How many miles are on this crank position sensor that you know of?

Take the LHS valve cover off. Rotate engine until TDC #1. You can tell if you are on #1, vs #6 by grabbing both #1 valve rockers. If they are loose, you are on TDC #1. If one is tight, then you are TDC #6. Once you are verfied TDC #1, Pull the dizzy cap off and see where its pointing at. It should be pointing at wire number one pretty damn close. I know these dizzy'* aren't exactly adjustable. A lot of people don't realize, when you drop the dizzy back into the engine, it actually turns the shaft when it meshes with the cam drive gear. You have to compensate for this by turning it back the other way a tooth or so then drop back in. It'* a learned procedure. By the time you have to do it again in a couple years, you will have forgotten it again.