There are indeed problems with DMA performance in a 4000, the easiest fix being adding some memory to the card. I remember doing the same thing with my A2091. There was a updated version (the A4008HC8) which had an internal patch I believe, but still it wasn't a sprinter.
Faaaastrom is basically the normal BOOT rom from GVP holding the gvpscsi.device. The improved rom you might be thinking of was the GuruROM by mr. Babel.
