Hello all, I'm new to the forum and have come seeking knowledge. I've searched the forum and the internet and could not find any information on the 99-04's regarding this. I've recently installed an Airaid cai on my 2004 Mustang GT with an MRT offroad H pipe and Flowmaster American Thunder's and a few other mods. I'm having it tuned by Bama and they are saying to make sure to remove the "reduction sleeve" on the Airaid for the tune to work properly. I have no idea what they are talking about. I thought maybe the "velocity stack" but then I wouldn't have anything to install the filter onto. Would someone please enlighten me as to what they are talking about? Thank You