Dual spark have 2 coils, so no....
Blocked fuel filter? Have you checked for vacuum leaks? Checked plug gaps, distributor cap/rotor, lead resistance/continuity, timing (And automatic advance if it has it - the vacuum advance distributors can stick in one position which cause all manner of problems) , air filter, airflow meter.
If you're going to replace plugs, only use NGK as the other brands tend to carbon foul very quickly in these engines for some reason. They also do a good oem lead replacement set for less than Nissan Genuine prices.
Also, if you change the fuel filter (Should be done yearly on every engine - but never is) run an injector cleaner or 2 through the system with good fuel (95+) and go for a good motorway run. I have to do an italian tune up in the 12 because the head carbons up if I drive around town alot.