The '99 Miata with the Sports Package included: Torsen® limited-slip differential, 15-inch alloy wheels with locks, NARDI® 3-spoke leather-wrapped steering wheel, front strut tower brace, front air dam, rear spoiler, and sport suspension with Bilstein shock absorbers, Hard S springs and 12mm rear sway bar. Power Steering was an option that could be added
The '99 Miata with the Leather Package included: power steering, 15" alloy wheels, low-profile tires, power mirrors, 3-spoke Nardi leather-wrapped steering wheel, door map pockets, cruise control, power antenna, Torsen limited slip differential, power door locks, Windblocker, tan leather interior, tan vinyl top and Bose audio system with CD and cassette.
In common between the two were: Torsen® limited-slip differential, 15-inch alloy wheels with locks, NARDI® 3-spoke leather-wrapped steering wheel, with power steering an option that could be added to the Sports Package. Both had AC as an option that could be added.
Items in the Leather Package not specified in the Sports Package were: door map pockets, cruise control, power antenna, power door locks, Windblocker, tan leather interior, tan vinyl top and Bose audio system with CD and cassette. These items can be classified as comfort and convenience components which have no effect on performance and/or handling and do not materially reduce the weight of the car (per the 13.2-A section of the rules). In fact, these options increase weight.
I plan to add the following Sports Package components to my Leather Package '99 Miata: front strut tower brace, front air dam, rear spoiler and sport suspension with Bilstein shock absorbers, HARD S springs and 12mm rear sway bar. I then would characterize this Miata as a Sports Package car with the additional Leather package items characterized as added comfort and convenience components. The Bilstein Shocks and 12mm rear sway bar are optional and may be changed per the E Street rules.
I consider this to be a legitimate configuration, but I want confirmation of this from the community. I don't want to go through the changeover and then be protested.
There is an outstanding issue in that the Sports Package does not specify leather seating as an option, and the 13.2A section specifies that comfort and convenience modifications do not include driver’s seat substitutions, so to be TOTALLY legitimate, I would need to replace the leather driver's seat with a cloth seat. I am hoping the local club(s) will overlook this anomaly, and would permit use of the leather seat. If not, and if I would intend to participate at the regional or national levels, I would replace the seat.
I think others may be interested in getting an official reading on this issue as well (if it hasn't already been dealt with), given that '99 Sports Miatas are very rare, and that even '99 Base Miatas with roll-up windows are hard to find. There seems to be an abundance of '99 Miatas with the Leather Package, and others with cloth interior but with power windows and locks rather than the roll-up windows and manual locks of the Sports Package. The latter would also need to be recharacterized to be legitimate.