Since it's an used car and you've just taken ownership I would just fork out some coin and replace all the spark plugs followed by a brand new set of coil packs.
If you're after straight plug & play a new set of Splitfires would be the best options, if you're into DIY and a tinkering, go with a set of LS coils.
I would avoid any other coilpacks that aren't OEM (new) or Splitfires. I've used other brands and they're all garbage once you start putting down some decent power, they all fail.