This may sound like a dumb question, but i always heard a dumb question is one thats not asked anyway here it goes. Can anyone tell me what a speed density system is?

 

Speed density is the system used on '90-92 F-body Tuned Port engines. It uses a MAP (Manifold Absolute Pressure) sensor instead of a MAF (Mass Air Flow) sensor. '93 (or '94) and up LT1's use both sensors.

On Third-gens, the MAP sensor is located just above the passanger side valve cover, hanging either off the cowl or the A/C box. It has an electrical plug and a vacuum hose connected to the bottom side. Its about 4" long, 1/2" thick and 1" wide (rough estimates).

Although most people prefer the Speed Density system because they can clean up the engine compartment more, it is the MAF system which can be modified much more without driveability issues. With the Speed Density system, cam selection is a much more selective deal because you have to keep good vacuum in order for the MAP sensor to operate correctly. Vacuum is also important on MAF systems, but you have a lot more room of play before you experience problems.