Truck Forums - 2000 Silverado 4.3l knocking

Hey you guys,
I got a 4.3l that spark knocks between 1000-2000rpm even under light loads. I had replaced the original Cental Port Fuel Injection spider assy a while back with the Multi Port retro kit and it improved the drivability greatly.
I saw somewhere that the computer is putting about 50 degrees advance in the ignition timing as low as 1200rpm, and I'd like to know how or where to send the computor to get about 2-3 degrees of timing taken out between 1000-2000rpm? The timing didn't have nearly as much advance at lower/higher rpm and I think its just too much in that range??
I've replaced TPS, ignition module, coil, distributor cap, plug wires & plugs, and thinking about the MAP sensor. Throttle body is clean. I've tried Seafoam too. Most of this was done before swapping the CFI to MPI. One of the MPI injectors didn't want to stay in its port all the way(#4) and might have backed out just a little as it didn't have any kind of locking mechanism I could see. Besides it couldn't move too far as tight as every thing under the manifold was. It didnt seem to mater if it wasn't air tight as it looked as if the surrounding area was subject to the same vacuum and it wasn't sequential injection, but I could be wrong.
I would think that if the injector was the reason for the knock that there would be a miss at idle or higher in the rpm range, but everywhere besides 1000-2000(worse 1000-1500)rpm it runs great? When it starts knocking I'll put my foot into it more and it seems to stop. Like I said under a light load its noticeable. I'm thinking that the MAP sensor might have the lower range of its potentiometer wore out?
Still like to take out some timing at the lower rpm in the computer I'm afraid its going to knock itself to death if I don't do something soon.
Any ideas or help would be greatly appreciated.
ssmonty