Natrually Aspirated model isn't turbo...
A turbo II has a big top mount intercooler above the engine as well. I'm not sure but I think you can put inject it through the spark plug holes. How old are the plugs because if they are really old you might want to have a pro remove them.
WARNING! Rx7's are notorious for having spark plugs break in half on removal due to heat! Guess where the side that your not holding onto goes... In your engine! Then you have to remove your engine and get out the half a spark plug. Take your time and do it slowly.
Rx7 Turbo II
N/a ~
The N/a doesn't have a hood scoop either...