Anyone wonder if it's because the stock MAF is calibrated for a panel filter and the KKM is a cone filter. (I am guessing you have a Non-SVT)

This is not the first time this problem has occured.

Okay with that out of the way - Barring any intake leaks that may have sprouted during install.

I would check & clean the IAT sensor & the MAF. Sometimes the filters are heavily pre-oiled...

2000 SVT #674 - Check it out!

Whoever coined the phrase; "If it ain't broke; don't fix it" ~ Just doesn't get it...