Wait, are you kidding me LOL.
Hey I'm not going to flame you (much) LOL, but you start a thread asking for our wealth of knowledge on the best mods for a budget of $2000 to $6000.
Asking which mods will...
"get more HP; from most economical to the more outragous"
Well, all I can say is you certainly picked the most economical mods, cause your fog light, GTR button, and emblems, ain't gonna be burning extra gas any time soon LMAO...
You might be lacking a bit from HP gains there though, and I'm guessing you still have around $5950 left in ya budget.
I know a great decal website if you want to get some "
go-faster-flames" next
Seriously dude, put that 6000 back in the bank, sell that Z, and go get a Honda Civic