SD does not give more power then MAF in stock forum. I don't know who told ya that but...no.

MAF runs in sequential injector firing, this means that the injector fires with the spark plugs. The SD system is called multi-port. It fires each bank of 4 injectors together, instead of each injector on their own. So it actually fires 4 injectors at once, even though not all 4 cylinders are ready to be fired. The fuel sits behind the intake valve before it opens and then is sucked into the engine. The MAF SEFI shoots the fuel right into the combustion champer when the intake valve is opened (way more efficient). I did a MAF conversion to my truck and it makes a noticeable power increase as well as a gas mileage increase from that power. The SEFI can better atomize the fuel being used which always equals more power.

Do a search on this site for "maf conversion" and you'll find a lot of information.

I just assumed that your 97 truck had MAF...as they started in 94-95ish on our trucks.

I have the ram air hood, it mostly helps with sound. To be honest, the mods you have done havn't really helped you that much. If you want to get into swapping intakes and changing the cam, do a MAF conversion. I have read a lot of books on Ford's EEC-IV EFI and MAF is definitely the way to go.

SD is pre-programed from the factory with specific engine parameters. It gives X amount of fuel for Y amount of throttle based on readings from the 02 sensor and a few others. It doesn't know how much air is actually going into the engine. MAF measures the amount of air coming in the engine and meters the correct fuel accordingly. Therefore, it's adaptive to engine mods (increasing the air flow through the engine can be recognized by the computer) and the air/fuel ratio can be more accurately perfected. Then you add on the fact that it's sequentially firing instead of bank firing, and it makes the engine more efficient with that power. You have to do a MAF conversion if you're looking into real engine mods. With the "mods" you have done (I don't consider an alternator an engine mod), you pretty much don't have any gains. The filter and TB spacer probably got you all of 2-3 hp, the underdrive pulleys probably 3-4, and the exhaust maybe 10. The coil doesn't help much on it's own w/o a high power ignition system. Wires/spark plugs, eh...not really an engine mod either. Your hi-amp alternator probably wiped out any gains you did have. If you want power, do a MAF conversion, swap the heads/intake/cam and away you go. Of coarse, an oil pressure and compression test should be done first.