what parts to buy: 6 Coil in boots & 6 ignition coils?

I don't know. After I replace the plugs and boots, I'll see if the engine continues to run rough - if so, I'll check the coils. It's a friend's vehicle - I've never worked on an Infiniti. It is good to know that there are only 3 coils instead of 6, given their cost. I do know she hasn't changed the plugs, so that could be the problem. Thanks!