At my old house, I was on the 8mb dsl, and outside the effective range. When I started, I paid for a 4mb connection. There were some hiccups and on occasion, whenever the phone ringed or I tapped the hangup, connection rate dropped down to a puny speed, though 4mb was still reported by the modem. My only effective solution was to move the modem to the basement where the telco wires came in, wire the modem right onto the wires, and I added 2, not 1, but 2 line filter in series before the phone line fed the rest of the house. It worked like a charm for 2 years and I had the best consistent connection in my neighborhood for 2 years. Then, when the telco offered 6mb, I upgraded and still everything was great. Then, during the last year, the telco upgraded all local 6mb connections to 8mb for free. Holy crap, my performance took such a nose dive, you wouldn't believe. I didn't know why since the 8mb upgrade was done to everyone without my notice. But noticing the modem reporting a 8mb connection a few days later, and realizing this was the cause of the crap, I had to call up my telco's ISP to demand a slow-down, limit my rate to 6mb. It took me a bloody hour to convince the damn tech that this was truly an improvement as he kept reading on his screen that I had an error free 8mb connection and it should be full speed now. Once finally done, everything ran at full speed once more.
Lesson, the techs don't know all the ins and outs of these stupid modems & their head-ends. There is a mix of wire lengths, wire quality, head end modems and home dsl modems with differing qualities and sometimes maxing thing out may read good on the modem tests and specs, but, this doesn't necessarily mean crap in the real world.
If you have an 8mb connection and modem, and you dont want to wire the modem like I said, or try a different DSL modem, I can only recommend asking your ISP to drop your maximum download & upload speed by 1 notch to see if that cleans up the data hiccups. Sadly, you may be in a situation where you need to do a bit of everything while there may not be anything your telco may be able to do to improve anything since they have to work by the 'book'.