Is the tach following the engine speed or is it bouncing around beyond what the engine speed is?
The tach signal comes from the ignitor. I think it's either that ignitor or the dist. base assembly that has the cam sensor in it. Only use Honda parts for ignition systems. I'd start with a Honda ignitor first then if that doesn't fix it change the dist. sub assembly. I know you've been given a new part but trust me I get cars in the dealer shop where I work all the time with new non honda ignition parts like ignitors and they don't work. I replace them with my own "test" dist. or ICM or coil and it runs fine again. Since the tach runs off the ICM replace that first trust me.