I have installed the PCV and the AutoTuner along with the rear taillight run/turn switch and I have no room under the seat for anything else. The PCV came with a deeper bracket to allow a little more room but even then I could not get anything else under the seat. I am looking at adding the LED light kit but at this point I would hate to take the seat off again. Does anyone make a deeper box that fits down into the rear fender? That would give a guy a little more room. What did the rest of you do out there?