slow speeds on WAN interfaces

Hi Everyone, been using ClearOS7 for nearly a year after coming from PFSense
I have had this issue, from the beginning but I always assumed it was a hardware issue
I have 2 Virgin Media Business connections these present as two ehernet connection 5 IP addresses per connection
Virgin (being bloody virgin) do this using a tunnel in each router it's a strange way to provide static IPs but there it is!
so my two 500Mbs connections normally manage380 (ish) in reality
this is where things become more confusing!
I am using "multiwan" and the built in speed test per interface, never sees any better than 130Mbs
the far side of the gateway I am lucky to see 100Mbs
but if I connect a PC directly to the router (using the same IP address and subnet as i am using in clear) I regularly see 380Mbs??
I am using a quad gigabit eternet card in the ClearOS box with a 3GHz i5 and 8GB of RAM, the previous bos behaved the same, that used a core 2 quad at 3GHz and 16GB of RAM and as it was a re-used Smoothwall box (pointwell) it had six integrated Intel gigabit NICs it wasn't a huge deal with a pair of 65MBs PPOE connections we used to use (I could sometimes get the full 65MBs per connection)
but people are not too pleased with me, having signed up for 36 months per connection to VM and it doesn't feel "any" faster
love and peace Gazzzman