I have a Holley HP system on my 70 Challenger 440 EFI 6 pack and a FAST EZ 1.0 on my 73 Cuda 416 EFI 6 pack, the Holley is completely tunable whereas the FAST is not. Tuning can be scary for sure but it is not magic and with a little research and education you can do it reasonably well. Granted there is no replacement for experience but it is so cool being able to adjust fuel and spark from a laptop at any point in the RPM range. Additionally, you can tune your car remotely these days, either have someone write you a tune and install it or in some cases using wifi a tuner can tune your vehicle from anywhere. Yes having a dyno and a tuning it on one is the optimal way to go but the Holley system will self learn as well, so once you get a base tune in it, it will make adjustments on the fly as you drive it.