I used to work for car dealership, we had a problem (Carbon Tracking) - so everytime we put wires on it, it would foul a plug & set a Check Engine Light. The GM tech bulletin stated the wires must be installed with "Di-electric grease" squirted into the wire cap then installing on the spark plug. What was happening is the plugs were actually shorting, and the porcelain cracked, & the spark was coming outside of the spark plug. Also a compression test is an easy check, if you have 2 cylinders over 100psi & the one is at 50psi - there's a problem. I run a Napa fuel pump & fuel filter on my '06 Apex-no problems. I change my oil every 100 hrs (synthetic 5w-30) and every 400 hrs, do plugs (NGK BKR4E gapped at 40mm) , fuel, air filters, chemical pump oil, & blower oil. Also I spray the carb with carb cleaner. We do have a problem with fuel boiling due to hot temps here - so you have to choke the hot motor to get a restart. Another thing I found is all the ground wires come loose at the left motor mount be sure it's good & tight. I'm running the original coils & wires from 2006.....