Well all MX6's are really 626 coupe's, They changed the name for north American and Australian markets.
All 626's are really Capella's, Mazda changed the name for some international markets.
So you have a 1988 Mazda Capella / 626coupe/ Mx6.
I'm sure that doesn't help.
But if you took off the name badge and called it any one of the 3 names you would be right.
All that being said because your car was built in Japan in Feb 88 and tagged in Australia in March 88 it was built for the Australian market and would be labeled MX6.
The engine should decide the cars name. For the most part Australia being the exception MX6's run F2 and F2T engines, most MX6's in Australia came with F2T engines but I have seen some members that had 2.0L 16V engines.
To the best of my knowledge Capella's and 626 Coupes don't have the 2.2l Turbo motor. Some got the 2.2l naturally aspirated but I don't think there are any F2T Capella's or 626coupes with the exception on New Zealand.
New Zealand has F2T Capella's and Australia has FE or F8 MX6's.
I haven't found 626coupe's listed as having F2T motors yet. But there might be some country's they where sold as 626coupe with F2T's (maybe Germany).
There are so many variations of the 1987-92 GD platform (which was sold until 1997 in some countries) some country specific, some options...
Here are a few of the badges that can found on GD's