Is there a method of testing my ISP for burst throttling or for that matter any sort of bandwidth or limiting of certain websites, for example when clients stream a utube videos the progress bar starts very good but stops and pauses then resumes, it is like utube server is overloaded and giving data in short bursts but I have tried this at several times and my bandwidth being used is less than 50% of my ISP allowance, I checked MTU and 1500 appears to be the maximum and PPPoE is 1480, any advice is most welcome.

it`s the same with my ISP - I think this is youtube servers bandwidth optimisations.

I have 20mbps at my home, and still have youtube issues. It's a youtube problem, not ISP because Netflix works just fine.

Actually it is an ISP problem.
Youtube is hugely popular which for an ISP means they would have to upgrade their peering with youtube.
However many ISPs came up with the idea that charging twice for the same thing is better than charging once so they try to blackmail Youtube by saying "Either you pay us an additional fee for the traffic or your connection might start sucking...".
Google on the other hand has refused to do this so far.

What's going on there is the core of the net neutrality debate we are currently having.
Google actually has public stats about this: http://www.youtube.com/my_speed

Actually it is an ISP problem.
Youtube is hugely popular which for an ISP means they would have to upgrade their peering with youtube.
However many ISPs came up with the idea that charging twice for the same thing is better than charging once so they try to blackmail Youtube by saying "Either you pay us an additional fee for the traffic or your connection might start sucking...".
Google on the other hand has refused to do this so far.

What's going on there is the core of the net neutrality debate we are currently having.
Google actually has public stats about this: http://www.youtube.com/my_speed

If this be correct has the ISP to report to customers if asked they have any bandwidth limitations inplace?