Hi and welcome
First ignore the PN speedtester - the file size is very small and it wasnt really designed for the high speeds of Max - even PN will admit its not the best indication as it was originally designed when 512kb speeds were the norm.
One of the speetesters I prefer is the BBMax one which IMHO seems to be pretty accurate.
Theres a list of speedtesters here:-
http://www.kitz.co.uk/adsl/speeds.htmStrictly speaking the BTw speedtest should give you a good indication of whats really going on on your line - because it tests between your home and the BT RAS
The performance tester gives you some additional information that you cant get on other testers - but it traverses your ISP connection so should be an indication of "real world" performance.
Your IP profile is an indication of what your throughput speeds should be under perfect conditions.
Bear in mind this is Maxdsl and welcome to *up to speeds* where more than ever users are seeing bT let contention kick in at the local exchange. I dont think theres many people on any ISP that sees much over 4Mbish during peak time hours Im afraid.
BT defines acceptable speeds as per here;
http://www.kitz.co.uk/adsl/acceptablespeeds.htmTry running some BBMax speedtests and see what they tell you
Perf PN BTw
5341 1415 2546 19:30
3703 848 2594 10:00
5904 2135 2505 06:30
Those BTw speedtest do indeed look very weird - what is going on there I really have no idea - its almost as if for something like you say is cutting the speed at around the 2500 mark ??
If the results were the other way round I could perhaps point fingers, but not this way.
BTW with max it is possible to see variations form one min to the next if your exchange is *bursty* type congested... but what youre seeing isnt that either.
Try running some BBMax (rather than the PN) speedtests and see what they tell you.