OK, I have been looking for a bit now and the more I look the more confused I get. I see some sellers that list Flex as 90-97 and 99-05 and others list 90-05.
For instance, this seller has two model years in the drop down menu but both list the same part number. (Good price, too.)
Tein Flex Coilovers Mazda Miata !!!
This one as well. Same part number but different model years.
TEIN FLEX COILOVER 99-05 MAZDA MIATA- TE-DSM40-6USS1
The only thing definitive that I have ever seen is on Adrenaline Racing's website.
"As an additional option for owners of a 1999+ (NB) model Miata, TEIN offers the EDFC (Electronic Damping Force Controller). A small control unit is placed within the car (about ¼ DIN), which allows you to adjust the damping force from the drivers seat. Up to 3 different settings can be stored, allowing you to recall a different setting for track use, street use, or another driver with the simple press of a button. You can also ‘lock’ the EDFC to prevent misuse by another driver, or accidental adjustments. A must have for the high-tech connoisseur. "
So that being the case, is there really a difference between the NA and NB models if I didn't care about the EDFC? I guess what makes me wonder is that you rarely see used Flex come up for sale that were NB specific and the set that I posted up last week on egay went for a reasonable price but were listed for an NA.