USPS api rates: All foreign and domestic rates correct except for Airmail Letter Post

Hello!

I am having trouble with the usps api rates.

Everything works flawlessly- I get all the correct rates foreign and domestic except for airmail letter post: each country is slightly more than it should be ie based on 1.3lbs: UK should be $10.40 is $11.60, Japan should be $11.60 and is $12.95

whats up?

I have my Tare at 0 and no additional shipping and handling fees, I have called usps, and they say there servers are dishing out the correct rate to zen cart. I have a fresh install of v1.36

here are the shipping methods I use: Domestic Shipping Methods
Priority, First Class, Media

Int'l Shipping Methods
GXG Non-Document, Airmail Letter, Airmail Parcel

as it turns out 60% of my shipping is Airmail Letter, so I need it to be the right rate.

Any suggestions?