>>19
try to figure out how much exactly it lags and adjust stepmania's global offset accordingly

in stepmania\data\stepmania.ini find the GlobalOffsetSeconds=0.000000 line and change it to whatever

if you need to find a value, try finding a stepfile that you know to be onsync, then set it to auto adjust and play it on the pad. auto adjust is used when making a DWI/SM file to find the gap (millisecond offset for the song), and basically takes your input and changes the gap so your input is perfect. this is a pretty bad description, though. you can probably find a tutorial or a help file or something on stepmania.com about fixing pad lag.