If it hasn't limited by the modem, you could just saturate the connection up to where it's limited when uploading For cable modems, the modem runs the ISP's fi

If it hasn't limited by the modem, you could just saturate the connection up to where it's limited when uploading For cable modems, the modem runs the ISP's firmware which downloads runtime parameters from the ISP. The supported modem list is modem's they have firmware for that run on their network Afaik it's not very difficult for the ISP to detect modified modems