Well, it would be 2^(7*8) = 72057594037927936 possible intros. Someone/something has to generate, run and evaluate them all. Theoretically it's the "halting problem" all over, to wait for the "final output" of each intro. The 16 byte effect for example takes a while to achieve its final form. So even if it is somehow managed to evaluate 1000 intros per second, we are looking at about 2 million years of time to really test ALL possible 7 byte intros.
I think there are some standard header bytes, so the number of combinations of the interesting parts might be much smaller. Also I said less than 7 bytes, so it's actually 281474976710656 . If header bytes reduce 1 or 2 bytes, it will be 4294967296 - 1099511627776. 1099511627776 / 1000 / 60 / 60 / 24 / 365 is around 35 years.
