For the most performance, I have gone through a lot of tuning with carb and timing curves, pump cams, jets, squirter nozzles etc. The carb was modified with different boosters. When I got done, with the tuning, the engine had nearly the throttle response of fuel injection. I always said then that I had better know where i'm going when hitting the throttle so there is no-one in the way because the car would just move beyond belief. Then I went fuel injection and sold the intake, carb and cam. It's all just a memory now. The cam is now much different than with the carb setup. The FI setup has a much broader power band with a wide lobe center vs the single pattern more narrow lobe center that I used with carburation. There is a lot of understanding to be gained in the relationships of timing and fuel control that should be understood in order to make the changes come all togather. I have an old copy of the Holley carb book that has info not given in most present day books, on tuning. It has graphs on pump discharge vs the cam profiles (colors), the various secondary spring charts, How to drill the primary throttle plates and setting the plate angle to get the correct idle and off idle response, and power valve selection. To do it near right take a large amount of time and record keeping so you can return to a previous setup and go to a different change. All this includes tailoring the advance curve with springs ,weights and stops. A possible problem one could have is at idle, throttle plate being to far open and allowing vacuum to start pulling advance in timing to far. Most of the time, base timing is set with the vacuum disconnected. In a FI engine the base is 10* with the plug out and goes to 20* as a norm. During cruise, the EGR opens, timing goes advanced and fuel injected is greatly reduced. This is one area were better fuel milage comes from with these engines. Also in FI, the timing can go as high as 48* under certain conditions. This brings another point I have a hard time getting people to believe and that is rotor phasing in an FI engine because the rotor doesnot move as in a carbed engine so it has to be correct to handle timeing ranges that wide, without cross fire because it is electrinically timed and is one of the reasons the rotor has such a wide tip as opposed to a points type distributor. The tools needed to effect an optimum setup are a dial back timing lite, hand vacuum pump, vacuum gauge, info and test driving and still it's seat of the pants but you know when its better and when its not.
