For your info, using the modem manufacturer supplied drivers often causes this type of problem for people who have used the Windows generic driver previously.
While the Microsoft generic driver works OK, it shows a theoretical connect speed only (Usually 115K, the setting of the max transmission rate) while the correct driver/string indicates the actual connect speed to the line.
There is no difference in performance generally, however you may gain some by using the correct driver.
The connection speed you quote is very good for a standard copper phone line actually, and it will vary depending on the line through the exchange. If you have a poor connect speed, it may help to reconnect again. You may find the next line you get (random selection in the exchange) may be better.
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When all else fails, read the manual!