Have you tried to put it back into original state (without extension) and see if the speed does improve ? I have seen couple of times people were doing DIY extension using standard coaxial cables (the ones for satellite dishes, etc.) and power levels were flying through the roof and the speed dropping drastically.
Also which type of cable did you use? RG5, RG6 , double screened, triple screened or maybe other ? Depending on extension length, it may be necessary to install an attenuator as well.
IMHO the best way would be to get a VM engineer to sort it out for you.