I found an 'interesting' change in the aircraft.cfg file.
My favorite planes in FS9 are the Hawker Seafurys by David Hanvey/Paul Barry/Jerry Beckwith. So, I decided to see how well they worked in FSX. I had 'played' with the .cfg file to add smoke to all of them, and had it working in FS9. However in FSX, when I hit the smoke button, I found that the smoke appeared, BUT, it was at one wingspan above and below the plane ???

I opened the .cfg files for the default EXTRAs, to see if I could find what was happening. I found that for some reason, MS changed the way the smoke parameters are read. The first parameter in FS9 is the VERTICAL one and the last 2 are HORIZONTAL. It is the opposide in FSX. Once I changed the Seafury's .cfg to match the Extra's format, the smoke appeared at the proper position.
Here are the Extra's FS9 and FSX smoke entried for comparison:
FS9:
[SMOKESYSTEM]
smoke.0=0.00, -0.70, 1.40, fx_smoke_w
FSX:
[SMOKESYSTEM]
smoke.0=-10.00, -0.70, 0.0, fx_smoke_w
Now, if I can just figure out why the CANOPY on the Seafurys doesn't display I'll be a 'happy camper'.