1centgts4

could try checking throttle body seals, rough idle can be caused by a stuffed seal or 6.

fitting 'bigger' brakes will do that, your ABS kicks in sooner. Can test by pulling the fuse on ABS, will confirm it's your abs and not a warped disc etc.

hmm, still sounds like a pipe has come loose, have had this happen to me a few times in silvia/skyline, exact same issue was due to a pipe coming off turbo, may look like it's on but.. air still may be escaping, doesn't take much when it comes to compressed air