computer chip upgrade

I just want to ask what chip out there is good and if there are any web sites I can see what fuction does the chip do and the difference from the stock chip.

I need to know the info in details not just general info such as it will give me whatever power gain and more fuel delivery.

I recall an article I read about the mugen chip is running open loop at all time (correct me if I am wrong) which what I don't want.

For those who had changed their chip please give me your feedbacks only if you know what you are talking about. Sorry, if I have offended anyone, but I am trying to get intelligent info, not another BS link.

Thanks in advance