Yes, the valve does offer some restriction, but by itself or with the addition of a very free-flowing in-line filter provides sufficient flow for the Valk. You have choices on powering it. Some people use a small relay that is good for a couple of amps and trigger the relay from the ignition coils black/white wire. Others, myself included, don't use a relay. I ran a wire back to the 5 amp auxiliary power circuit underneath the right cover and this works well. When powering the solenoid directly from the ignition coils it sucked too much power and starved the coils at high rpm

causing a bad miss.