Lack of Power/Sluggish/Spongy/Stumble

1. Air filter dirty or plugged
2. Improper ignition timing.
3. Fuel filter restricted.
4. Contaminated fuel.
5. Improper fuel pressure.
6. Improper EGR valve operation.
7. Improper alternator output voltage.
8. Improper valve timing.
9. Improper compression.
10. Worn camshaft.
11. Improper secondary ignition voltage.
12. Restricted exhaust.