That sounds like a rod knock, as in the connecting rod bearing has failed. If you had water in the oil from a leaking head gasket, it could ruin the bearings as the oil will float on the coolant and get picked up by the oil pump and pumped through the oil galleries.
The shaking seems as if you have a dead miss, as in 100% misfire on at least one cylinder.
Did you find much coolant in the oil pan? Did you drain the oil when you replaced the head gasket? If not, it is likely that coolant was leaked into the pan when the head was removed.
I would check the spark on each cylinder, and do a compression test on each to determine if there is a mechanical cause for the problem. A bad COP will cause misfire, but likely not the noise. Have you checked for spark on each cylinder? If not, that would rule in or out the plugs and COPs as possible causes. You replaced the injectors, so likely don't have a problem with them, but could have a problem with the wires that make them squirt. Check for voltage on each wire with the key ON, engine not running. You should be able to measure voltage on both wires. When the computer supplies a ground to one wire, it makes the injector open the valve and squirt some fuel. The computer takes away the ground when it is done, so the wires should both go back to 12v.
tom