@danvignau It appears you didn't read the first page of this thread:
As to why the fuse makes a difference, its easy to measure. Its the AC voltage drop across the fuse. Because fuses have to heat up in order to blow. as the amp is playing peaks, the voltage drop increases. The contacts on the end of the fuse make a difference too- which has led to the idea that fuses are directional (they aren't). Its just that sometimes the fuse sits better in its holder if you turn it around (although by simply rotating the fuse you can get the same effect, which can be seen by a reduced voltage drop across the fuseholder).