My air filter top has the bowl in the middle.
Of concern also:
Smoke analysis
White smoke: Caused by unburned fuel passing through the engine. Some white smoke is normal on cold start-ups.
Excessive white smoke could be an indication of inoperative glow plugs, loose injectors, low compression from worn rings or bent connecting rods, or coolant leak into the cylinders. Black smoke: Caused by excessive fuel for the amount of air drawn into the cylinders. Some black smoke on hard accel or at higher altitudes is normal.
Excessive black smoke could result from restricted intake or exhaust, inoperative leaking or weak turbo (if equiped), intake manifold gasket leaks (turbo), leaking or worn injectors, fuel return or supply restriction, advanced injecion pump timing or defective injection pump. Blue or blue/white smoke: Caused by insufficient fuel or oil consumption. Normal when engine is cold or idling for extended periods.
Excessive smoke could be caused by air in the fuel, contaminated fuel, loose or plugged injectors, thermostat stuck open, oil consumption, plugged crankcase depression regulator valve, retarded injection pump timing, or defective injection pump.