Time to tune up?

97.5 GS. About 20,000 miles ago i did a complete tune up. Plugs, wires, air filter, pcv valve, gas filter. the plugs are Iridium. Supposed to last forever.... The wires were standard AC Delco. They look good. No cracks. Is it time to replace? How often should PCV be changed? Filter is K+N....How often should i clean it out? I also found there is a filter for the supercharger bypass valve but have never replaced it...any idea's? I also used Techron fuel injector cleaner. Does this stuff really work, and how often should it be used?

Everything should still be good. If you live in an area that is exceptionally dusty then you may want to clean the air filter but K&N says 50K miles. The fuel injector cleaner works but you should use it according to the manufacturers recommendation. Most gasoline contains detergents today that keeps things clean so these additives just give it a boost. If you start getting misfires new wires and a professional injector cleaning may eliminate that but not necessary at this time.