From the top, sacs vs vco are the format of the nozzle. Vco is reg lb7 and the needle in the tip has to seat perfect every time to spray and to close off fuel. Sac however is the new style that has a bottleneck before the needle valve so all the actual pressure is concentrated on to hardened surfaces as oppose to an entire nozzle. Much less exposure and they flow more than the oem type so they don't have to work as hard thus making the last longer still.
All additive are not equal, if you put them on chart, Kleen would be like 3, and optic is 9. The best is biofuel but most people don't have access to it.
Liter pump, I personally have an air dog 2 165 and have run it for 5 years. I burnt one pump in the air dog but the fuel system is closed and as long as there are no leaks you will draw fuel through the pump. I can explain the fuel system later if you don't understand that part. Basically that filterhead with the hand pump makes a vacuum and draws fuel from the tank and supplies it to the cp3. No that is a long way to go for a little hand pump and they fail quiet often. Also or cp3 drinks a lot and the stock vacuum barely gives enough. If you tune it at all then you will need a pump. Also the pump helps maintain even pressure at the cp3 so the cp3 lasts longer and provides the exact pressure to the fuel rails from the lifterpump. The pump pushes fuel into the line so the system is pressurized instead of under a vacuum. Haveing it pressurized makes everything work a little easier. Main providers are air dog or fass. Both are good and both have merit though everyone will say one is better than the other.
Efi, google kory Willis, buy an auto cal from him based on what you decide to install and buy the appropriate setup. He will write specific tunes for your truck and keep everything running well from an electronic programming prospective.
2004 Silverado Cali lb7, Airdog ll 165, fresh sticks at 325k, DSP 5 on v2 by Rick Fletes, 33x12.5 nittos at on 20 inch American Racing wheels, modded factory air box, Profab Intake Horn, Batmo Wheel, Turbo port and polish, Full EGR Removed w/ fed belt, 3.5 inch MBRP Downpipe, Full five inch MBRP Exhaust, 10mm lbz cp3 pump, Dual Yellow Top Optimas, High Output Alternator, Cognito Pittman and idler w/ support kit, Cognito Contol arms, Drilled and Slotted Rotors on all four Corners, Custom Y Bridge.