If the plugs are indeed stock/stock gap, that will NOT work with a tune. You need to have at the very least, plug gap set to 0.030 (I believe Torrie likes 0.028) and plugs changed regularly depending on how fast this gap grows. The NGKs from Torrie or the Motorcraft SP534 plugs should work fine as replacements. So add that to the work that needs doing before the MKS is able to run smoothly again.