If you dont have a mazda compression meter....stick your finger inside the leading plug holes and feel the housings....if you feel any groves....run the other way.
Also...smoke on start up is normal as long as it's a little bit. Since rotaries use oil injection...there's allways some chilling in the housing to get burt off.
For water seal leaks...... Start the car with the rad cap off....look for bubbles....if you see any...the water seals are on their way out.
Boost controll.....look for the normal 7-10-7 (I think...it's been awhile since I'v been under the hood of a non singled-FD
)
Make sure the fuel line recall was done
A big factor in your buying price should be the interior condition. Mazda stoped making interior peices for LHD FD's. Interior peices are getting pretty expensive.
Let me know if ya need anything else.