What are the requirements to be at a Stage I, II, III, III+? What do you have to have put into your car to be at certain stages?

Please if you know, just do like,

Stage I= blah blah
Stage II= bleep blaah dee daah
Stage III= doo dee deeyaah poodee

thanks.

I have an '02 A6 2.7T, 6 speed MT, Custom Dual Catback Exhaust, Synchronic BOV's, K&N Filter, Short Shifter, Custom Turbo Pipes. Stock Turbo's and Intercoolers. What stage would I be considered at?