I think they come with the stencil. I dont mind either way. The reason why i got it is because i have Stett CAI and Charge pipe and i dont have to cut into my bumper. the guys there are awesome! they gave me a $50 discount to help with shipping. Plus they gave me these intake cover blocks for free when i asked for it.
The best way to go about ordering stuff from stett is to email them directly because shipping is expensive if you order from the website since they use FEDEX. I emailed them and they agreed to ship all my items via usps at a discounted rate. does take a bit longer but its worth the saving. Just say the guy with the orange pipes recommended you ;]