Sound offs. You had classes and strict rules. So for example in one comp you had to use an amp with no more than 20w per channel (with combined 40w bridged) then design your car around getting as much SPL (sound pressure level) out of it as you could, with that range of amplifier.
However, those like me (who were in the know) would use what was called "the cheater amp" and get banned
So why was it the cheater amp? well, there was a certain Phoenix Gold amplifier released many years ago. It was called the Phoenix Gold MPS 2220. It was so over designed and over built (triple gold plated PCB traces) that it could handle about twenty times that power. Then someone realised that if you played with the inside a little bit the amp could run at 1/4 of an ohm.
So think about it like this. The amp is made to run at 40w into 4ohms. However, theoretically (some is lost in heat) each time you half the ohm load you double the power. So at 2 ohms it would put out 80w. At 1ohm it would put out 160w. At 1/2 an ohm it would put out 320. Drop that in half again? you are talking 600 watts.
And that's why it was called the cheater amp and eventually banned from competition
I joined Team PG when I got to the USA and met all of the guys who ran it. Awesome bunch. If I can find my old comp pics I will upload them.