I've installed six of these systems over the last dozen years or so(Ramjet, FAST TBI, FAST port injection, Holley TBI and an older Accel system that was NOS). Here my $.02: without controlling the spark directly from the crankshaft, port injection does not offer any benefit over a throttle body system. Controlling the spark from the distributor is just not accurate enough to extract the benefits from port injection. I would stay away from port injection unless you have an ignition system that is crank-fired and controlled by an ECU that is cylinder specific. The benefits just do not outweigh the cost and complexity.
Any type of self-learning system should be good as long as you have the wide-band O2 sensor included--just make sure you engine makes the required vacuum. If not, you may have to switch to a tune it yourself system and some expensive dyno time.
If you want to make a bunch of power, have good reliability and are the set it and forget it type: I'd use the FAST TBI or the Holley TBI. The systems I used and installed were as good as any carb, got equivalent mileage on the road of a Quadrajet, but had great throttle response, not to mention the cold-start benefits. Just make sure you get the wide-band O2 sensor/upgrade. I currently have an older FAST system on my DD and it has more than 72K miles, runs on pump gas and puts out close to 480HP and gets nearly 24mpg(400sbc, flat-top pistons, AFR 195/old style, zz430 cam replica with Rhoads lifters/intake only and 1.6 rocker/intake only--[my brother has this exact same combo and makes more power with a 107 LSA cam with longer intake duration, but equivalent lift and does not have to use the Rhoads lifters or the 1.6 ratio) the correct camshaft makes all the difference and saves you from the Band-Aid approach I took].
For a mild 350-383 the Ramjet I installed was also GREAT. It now has the Arizona Speed and Marine upgrades, and is fantastic: truly a great everyday driver system, but is HP limited. I think this system is a no-brainer if you want 400hp or less. It is factory tested, has OEM reliability, and GM has worked out all the bugs as long as you use a fuel system with a return. A few times a year I get to drive the Corvette I originally installed the system in nearly a decade ago. Every time I remark to myself how well it runs and how good the throttle response is.(350, fast-burn heads, 385 fast-burn cam with 1.6 intake rockers)
For any system make sure you have a good fuel pump, regulator, and a return fuel line. The variable pressure systems are actually not as good as a carb in my experience. (I put one in and soon upgraded because of its poor performance. Later, a friend bought one against my advice, he had to upgrade too.)
I hope this helps