Lots of things but I will start with this... have you read this thread?
http://fepower.net/simplemachinesforum/index.php?topic=227.0 ...I've been where you currently are and trying to get.
I just read it, and I've seen one of your other postings, few around my area said if wanted to make bigger numbers go with c4s and then I read one of your threads on your build and that kinda sealed the deal on trading my d2s for the c4s, I find it rare to see many standard 390s making 500hp + and you seem to know what your doing for sure
