Slow booting ttp8

Hello,
just bought a second hand IMAC 27" and got El Captain . I bought a 32 GB usb key and installed el captain and ttp8. Like I did with lion except it was a 8GB key.

First behavior is a password to access the disk; then a second one to open the session.
Second behavior when clicking on ttp 8 or anything is takes about 10 mins to open! which never happened with previous bootable key.

so is there a problem with el captain ? TPP8?

thanks