i think you just go to a mechanic who is qualified to do an engineers cetificate... there is no other way around it i dont think mate...
why what is defective on ur car? because u know that if there is something on ur car that's defective, ie the cops give you a defect notice then you have to change it back to legal specs before getting the engo cert...unless you have a dodgey fella mech.

sometimes these can cost a lot of money too, more than expected anyway...

is this any help?