Hey, interesting situation you've got there! It sounds like the upload speed drop might be due to the change in your service package rather than the modem itself. Even though both "Blast!" and "Fast Internet" advertise up to 100MBps uploads, there might be differences in how they prioritize or manage speeds. Have you tried contacting Xfinity to confirm the current package details and whether there's any restriction on customer-owned modems? Sometimes ISPs have specific settings or firmware updates that could affect performance. Also, maybe double-check your modem's compatibility with your service plan. It could be a simple config issue!