If I remember correctly the only difference between v90 and v92 is the upload speeds that the modem can achieve. Therefore this shouldn't effect your download rates and leads me to think that the problem could be elsewhere.
Could be that your ISP has a high ratio of users to a line. Check this out with your ISP. Some cap at 50 users to 1 line but others don't. Sorry if this sounds a bit confusing can't think of the right terms to use. Basically some ISP's put a high limit to the number of users that can use 1 of their connections to the net. This can cause you to how slow download speeds and slow down your general surfing.