what plug are you guys referring to?

 

you know, i bought the motoworks slip-on, a K&N, and removed the spark arrestor in my Z, and i don't get any backfiring or anything, but damn did i lose power...i used to be able to pull the front end up in 3rd with a little elbow grease, and now theres hardly a chance i'll get it up...anyone have a similar set up? which jets did you use?