Diesel loco performance

Hi all,
Have downloaded from the Steam4Me site and installed Diesel locomotives NSWGR4206, VR B60, VR B74 & VR S300.
Each locomotive performs as expected in MSTS however when operated in Open Rails they lack speed with typical performance
seeing a maximum speed of say 32mph @ 100% on reverser then falling away to 12mph and remaining there for the most part.

'Research' at Train-Sim.com revealed this post:
http://www.trainsim.com/vbts/showthread.php?319275-Underpowered-Power
which includes a referral to
http://www.trainsim.com/vbts/showthread.php?306136-How-coupling-works-in-Open-Rails
I have applied each 'fix' however unlike the original poster have seen no improvement. I have also installed cg804a.zip an E class
locomotive of  similar vintage although constructed some 5 years after the Steam4Me units and this locomotive performs
satisfactorily in MSTS and Open Rails. As a last resort I compared the Eng. files looking for any obvious discrepancy with none
evident to my untrained eye.

The locomotives in question were constructed in the early days of MSTS and perhaps are not compatible for whatever reason
however I have not experienced this problem previously and am curious as to why all four units which no doubt share commonality
wont 'march'. In other aspects ie. appearance, sound etc they load up in Open Rails.

Would welcome any suggestions to see the MidEastPlus locomotive roster injected with some Downunder know how.
Cheers
Duncan