if ur p1 (the red ones) theres no modifications that can be done that increase hp.
so yes suspension upgrades are fine among anything else that dosnt increase hp.
u cant change the muffler because it has the potential to increase hp. no pod, no ecu, no injectors, no exhaust modifications wat so ever.
if your on your green Ps then the 125kw/tonne high powered rule ratio stil applies. and u can mod the shit out of your car as long as its legal. (arguable)
everything else you need to no is here.
http://www.arrivealive.vic.gov.au/node/196
in conclusion if your Green Ps, your f*ked
Red Ps, your really f*ked
stay away from modying until u hit ur fulls is the best bet. but if you think u can handle risking 1100 fines and 3 demerit points everytime u get pulled over, then good luck buddy.
ive been lucky enough, hopefully you are aswell.
when did you get your licence buddy?
this way we can tell u exactly what you can and wat you cant do