polini you have to case port match, the biggest problems with polini kits is the intake side seizing cause you you to port the channels to help the boost ports flow.
kstar is more solid for the type of build you want to do, but if you want shit to last, your gonna have to work at it, and kstars are shitty cheap casted cylinders that need major chamfering on all the ports,
no offense, but are you lazy or you arent comfortable doing it
send me your cases and kit, i'll case port match them and rebuild your e50 for super cheap.... polinis are expensive but when built right there faster then any kstar, but kstars are cheap and pretty awesome kits when cleaned up....
email me if you want help, i'll take the time to walk you thru it buddy, i remember when i had my first beer.... jk