Ashrae Duct Fitting Database

I know this has been raised before but the thread is now closed
I've set up a duct system and used revit MEP to calculate the pressure drop through the system. I have also done a check calculation manually and the fittings Revit MEP is using is different ASHRAE fittings to those it should be using. For instance for a mitred bend Revit uses CR3-17, which is actually a Z shaped elbow and not CR3-6 which is a mitred bend. At the moment some of my systems are over calculating and some are under calculating the pressure drop by around 15% in revit. This doesn't give me much confidence in the output from revit.
Is Autodesk going to fix this bug? Is there a way to assign the ASHRAE part by type? The way it seems to work is that the fixture is specified as a part type - elbow for instance, and this then pulls up the ASHRAE.xml file which has a program which defines the part based on the size, flow, angle, etc. which would be fine except that it doesn't seem to be working. Is there a way to manually override this in the fitting? I can't find where you would add the part type as a parameter in the types or element properites that you could then change by instance.
i managed to schedule out the pressure loss by system section, but every time i try to schedule out the part types for the system it comes out blank. Also, are the revit MEP calculation algorithims approved by ASHRAE? Have they been checked by ASHRAE to be accurate?
If anyone has any help or if anyone at Autodesk is reading this - help!