You never get any really appreciable power gains from most items. Really maintenance and avoiding loss from ware and tear is best.
Correct plugs and gaps
Clean TB and IAC
Proper fluids and levels
Clean your battery and ground connections.
Run engine above 3300 rpm every 10k mi or 6 mo whatever is shorter.
Proper tire pressure
Correct gearing to tire size ratio.
If you want more power, look into a stroker, turbo or super charger, or a 8 cyl swap.