If you are bidding on a newer Mazda Miata -2007 or 2008 from outside your state be aware that because of new emissions laws you may be unable to register it in your state.
If you want to register your Miata in California, New York, Vermont,Maine or Mass., your state requires that your Mazda Miata has the "CE2" emissions option. This is also known as "ULEV". If you overlook this and for example, buy an 07/08 Miata from Texas and try to register it in say California, you'll be in a whole world of problems because you won't be able to get a legal registration for it and it wouldn't pass a Smog test. At best you'll have to re-sell it to a non-ULEV state. It is much wiser to ask the seller for a copy of the options list on the car before you bid. Confirm the CE2 option is on the car by getting the VIN and checking it with MAZDA to ensure the car you are bidding on  has option CE2 if you are in an ULEV state.You need written documentation for this before you bid- a verbal assurance from a smooth salesman in Texas is no good at the California DMV!
It is possible that an 07/08 car for sale in a non-LEV state has the CE2 option but guessing wrong will be an expensive and easily avoidable oversight.
If you buy from within an LEV state that doesn't guarantee that the Miata has CE2.It might be someone trying to unload an out-of-state car that they can't register. Be wary of any Miata being sold from an LEV state that has non-LEV state plates,dealer plates or no plates at all.Just ask for a copy of the options sheet for the car and run the VIN with MAZDA. A good digital photo of the VIN & emissions plate may be helpful too.
In theory it may be possible to retro-fit a car without CE2 but I could find no official information or cost  on this procedure. Who would certify the modifications ?
Follow this advice and you could save yourself thousands of dollars and much grief!