Sorry for the late reply. I don't visit this site often and I forgot about this thread.
The possible frequency range of the hsv is much more narrow than the shurflo pump's. It can only operate at 100 Hz or so, MAX. This is because the width of every pulse must be long enough for the valve to fully open and fully close. Depending on what hsv you use, this takes approximately 3 ms. If the frequency is too high, the valve will simply stay closed at low duty cycles, and stay open at high dc's. It will not be able to modulate flow variably.
The shurflo pump, on the other hand, is not restricted in this way. The pump simply needs to be on long enough for the motor to begin moving. Because of this, the shurflo pump can operate at much higher frequencies.
I don't have first-hand experience with the shurflo pump's longevity in pps kits, but it makes sense to me that it would wear out quickly from the constant changes in pump speed.
As mentioned earlier, the pump can actually operate at HIGHER frequencies than a fuel injector/hsv. You MIGHT be able to use the AIC to control a shurflo pump, but the pump will need to draw 10A from it. If it's not designed to provide that much current, you could fry the AIC. Otherwise, it should work. However, the AIC will be perfect for a hsv.
You are right, a pwm controlled pump is not that accurate. People do get away with it, though. But since you already have something suited for controlling a hsv, that would definitely be the path I recommend. It will be much easier and less costly to go hsv now rather than going the pps route first.
I am in the process of building my own WI kit from scratch. If you need any advice on parts (where to buy, how much, part #s, etc.), feel free to ask.
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