I did some further examinations and happened to figure out that it works well with object constructed in MOI but extruded. So as I exported it as .STEP all dimensions are correct but as soon as I have extruded that 2D draft constructed in MOI inside MOI and exported it things will went wrong and for some reason whole object will be doubled by its size when imported.

I draw every part by using draw tools and then trim, extrude I did not use any primitive solid forms like sphere, cylinder etc. I guess this has nothing to do with exporting dilemma but in case it will help I thought it´ll be wise to mention.

Regards:
Mike