could ipxe be causing slow windows boot speeds?

[robinsmidsrod]

You can enable syslog logging in iPXE to get more exact information on what is happening without having access to the console. You can then build with DEBG=int13,scsi,iscsi to see the timestamp when iPXE no longer is communicating with the iSCSI server. That might give you some ideas.

I would capture packets on the iscsi server when the machine boots quickly and once when it boots slowly and carefully compare them to see if there is any difference in the iSCSI conversation between the two traces. I'd also try to increase the log-level in Windows and carefully look through the log files in generates about boot-time initialization (not sure how to do this, but you'll probably need to modify the BCD used).