I currently run the Std STI5 JDM heads and cams.
The block is 2.5L , turbo is GT3071R.
What I want to acheive is increase the horsepower but keeping or increasing my low end torque, so what camshaft should I go for?
I see so many and I am confused.

Is there anybody with personal expirience with aftermarket camshafts?

Will AVCS help at low end torque? Can I convert my existing heads to AVCS?
My MOTEC M800 can tune this.

 

Well I know nothing about your turbo or the 2.5 engine, but I know as far as camshafts go, anything hotter than what you've already got will gain you power at higher revs at the expense of low/mid range torque and flexibility. That's just an unavoidable rule of cam selection on any car unfortunately, unless you have some kind of variable valve timing/lift system.

In other words you would probably be better off leaving the cams alone IMHO. No doubt there are plenty who DO have practical experience of this though.