This is what has been working for me to "bypass" the throttle. It at least gets me HSPA+ speeds.
I'm using the Rocketeer ROM and I changed the APN and also forced the Network Mode to GSM/HSPA (Auto Mode)
The APN settings are:
Name: HSPA+ ATT
APN Type: Internet
All other settings are default. I also am NOT on 2.3.6 and noticed when I updated the APN didn't work anymore, so I went back.
I also have the WAP Cingular built and have working MMS.
Name: ATT WAP
mms proxy: wireless.cingular.com
mms port: 80
apn type: mms