Hello eo2am
I am from Spain, and of course, I live there.
In Spain there is a periodical inspection of vehicles, similar to the MOT, but not annual. Well, only annual for very old cars, like my CRX.
As people above has told you, there will be no problems if the car is US registered and then when it comes to Spain, it is registered again here. It would be different if the car comes directly from Japan. Then it would be a bit harder.
With US VIN, US registration, etc. they will ask here for a new inspection. You have not to worry about the engine, as in the engine is written "HONDA". They don't look for the code of the engine.
But, about suspensions (coilovers), rollcages, semislick or slick tires and wide body kits (including wheel spacers) they will look for it. If they find it, they will ask you about spanish homologations, that you won't have.
A heavily modified car can run in spanish roads, but you have to homologate all the stuff. And this is not cheap...
So, my recommendation: bring with you and the cars, stock parts like OEM suspensions and OEM ehxaust. You can get these changed here just to pass inspections. Once inspection of every car is passed, install these again.
If you don't have these parts, don't worry. Once you are here, get these from UK, as it is near us (cheap shipping rates) and they have all these parts available
Don't homologate anything, is a steal. Every time you pass a periodical inspection here, just take out all the "agressive" stuff installed on the car (coilovers, rollcages, wide kits, track tires...).
As for the engine, just make sure it is "silenced": OEM or nearly OEM exhaust. Or just homologate the exhaust, it is cheap if it is only this piece.
Don't worry if engine is not a B16B and if this has internals upgraded. They won't check it.
They will check sound of the engine (Db; Decibels), and the level of CO2 in the smoke of the exhaust. So, if you has a "stand alone" ECU, or any other type of
"mappeable" ECU (Hondata S300, for example), get soft maps every time you go for inspection.
If you come near Barcelona (north Spain), you can come to my workshop. If you bring with you the parts you want to be changed for the inspection, I will do it for you without problem.
We have here all the necessary tools and knowledge.
One question, is this an FD2 R?
Cheers ^^