Rusty,what makes you think he needs a coil? Ima thinking you need more sleep.
I mean OP could practically weld with the one he's got. I have never seen that behavior but coil would not be on my list of things to change, nor would an amp. I'd be looking into what could be telling the amp to fire like that, and of course I would be disconnecting the tach pronto, as others have suggested.
Since the engine starts and runs normally, Ima thinking the amp is being triggered by something else.
