How do HELOCs with high utilization rates affect mortgage FICO scores (FICO 2, 4, 5)?

[Elliot Wagner]

We have a few HELOCs with 97% - 99% utilization rate with balances in the range of $70K - $200K. How do these affect mortgage FICO scores 2, 4, 5? 

I keep reading completely conflicting advice where some sources say HELOC utilization rates don't affect credit scores at all, while others say they do affect scores significantly, and some others say that they don't unless you really max out the HELOC. Some say the impact is big, while some others say the impact is small.

What is the truth?