You should never touch the mid needle, (It should remain flush with the carb housing, it's the brass colored needle you can see in the picture) However, my CEN Matrix came with 2 upgrade needle's, and one of them is the LSN and the other is the mid needle. I took out my old needles, and noticed the rubber o rings were ripped apart.. I could also not get the car running with the new needles at all, so I put the o rings from the new needles back onto my old ones, and got her up and running.