yslow on phantomjs giving same grade A(98) for all sites

[ratan527]

Can someone help me,

yslow shows the overall score: A(98) for all websites. But the score is different for websites when yslow run from firefox.

Do i need to do any settings?

phantomjs yslow.js --info basic --format plain www.amazon.com
version: 3.1.8
size: 1.6K (1626 bytes)
overall score: A (98)
url: http://www.amazon.com/

of requests: 2

ruleset: ydefault
page load time: 30

phantomjs yslow.js --info basic --format plain www.msn.com
version: 3.1.8
size: 1.6K (1626 bytes)
overall score: A (98)
url: http://www.msn.com/

of requests: 2

ruleset: ydefault
page load time: 38

phantomjs yslow.js --info basic --format plain www.cnn.com
version: 3.1.8
size: 1.6K (1626 bytes)
overall score: A (98)
url: http://www.cnn.com/

of requests: 2

ruleset: ydefault
page load time: 133